Ball tosses on the serve are not straight up

That rule already exists, Wim.

Maybe the ITTF should drop that rule?

State that the ball should be tossed upwards, without the rule of doing so straight up.
I can't imagine tossing up in an angle can be that much of an advantage so it becomes a whole lot more difficult to return it. But I'm no expert ofcourse!  :-)

Throwing the ball in towards you does increase the speed of the ball hitting the bat quite significantly and will be an advantage.  The rule probably does need some alterations.

I wonder if any advantage in throwing the ball backwards is negated by the fact that ball has further to travel to reach the net?

I think the rule is problematic because everyone's idea of "near" vertical might be different. Is it 1 degree from vertical? 10 degrees? 30 degrees? It would be good if the ITTF rule had some clarification on what "near" vertical is.

It is, however, difficult for an umpire, who sits in the middle of the table, to gauge how vertical a ball toss is. The ideal spot to observe this would be on the side of the table in line with the table end. From the umpire's chair, the parallax effect comes into play.

I'm happy if an opponent is behind the line, throws the ball up and doesn't hit out of their hand :)

True Martin, the rule is difficult to enforce by the umpire sitting where they do.

You do get a fair advantage even though it is further back from the table.  Try next time, throwing the ball into the bat forcefully and see how much more spin you can generate.

The main problem with illegal servers I face are those that throw the ball pretty blatantly into their bat (i.e. at a sharp angle) to maximise spin.  One way around it, perhaps, instead of just calling for a nearly vertical toss (which is subjective) is to require the ball to be tossed higher...perhaps above head height.  It will be hard to do that and still put enough horizontal motion on the ball to aid spin generation.

Good day!
Even if tossing towards the paddle gives the person who serves an "fair advantage", does the serve become unreceiveble for the opponent? And both players can do the same. In any case, that rule and some others regarding the serve need to be changed asap! Adham Sharara should take a daily visit at pingskills.com!  :-)

I'd say we should add a new rule stating that the ball should be hit within a certain horizontal distance from where it leaves the hand. like 20 or 30cm. 

throwing the ball not vertically up can result in a very far away hit point from the throw point, which can be a distraction to fully observe the player's serve, since the opponent would also need to track the ball's falling trajectory.

and according to this 2 rule, if a player start with the ball arm laying flat on the table  
then it's most likely illegal already.

2.6.1 Service shall start with the ball resting freely on the open palm of the server's stationary free hand.

2.6.4 From the start of service until it is struck, the ball shall be above the level of the playing surface and behind the server's end line, and it shall not be hidden from the receiver by the server or his or her doubles partner or by anything they wear or carry.

I agree, in part, with some of these comments.  An advantage is only an advantage if it is not available equally to both parties.  I suspect the rule is really designed to reduce the number of points won on the serve (for the benefit of audiences rather than players).  I actually prefer playing a game with rallies to games with 20 serves and 20 missed returns too, even if I lose. The problem is, with a lack of well-crafted rules, we are left with trying to interpret and apply the 'intent' and this allows for even greater subjectivity and inconsistency.

However, any rule that specifies a parameter such as degrees of vertical or distance will be difficult to 'police' without a change in the way games are umpired.  The biggest issue here is the parallax error and the subjectivity, leading to inconsistency of rule application.  Do we add a 3rd official and have the assistant ump. (scorer) and the 3rd ump. sitting at the end lines like they do in tennis?

The primary breaches, in my subjective opinion, are against the “vertical toss” and the “resting on the open palm” elements.  Combined, these breaches enable greater speed of the toss, and the imparting of spin. All too frequently, players are allowed to let the ball roll into the base of their fingers during the toss while tossing the ball towards their torso, allowing them to 'flick' the ball towards themselves.

I suspect the best way to reduce the potential benefit gained from breaching the intent of the rules is to change the rule so that any attempt to breach will have minimal impact.  Changes such as the one suggested by Ji-Soo could reduce the effect of a less-than-vertical toss and even slow any spin created by the use of the fingers.  The only alternative is to make the existing rules more precise and more prescriptive, e.g. "throughout the toss the ball must not make contact with any part of the fingers of the toss hand, defined by the ..." or "throughout the toss the palm and fingers must remain unbent and parallel to the table surface", or "during the toss, the distance between the ball and the server's torso must remain at or greater than the distance between them immediately prior to the ball leaving the palm in an upward direction."  But do we really want these kinds of complex and highly prescriptive rules?

I play socially at work with players that have refused to learn and adopt the modern serving rules and still serve the old way - hands over the table, toss the ball into the bat.  I've learned to deal/live with it and adapt my returns accordingly.  They serve their way and I serve mine.  My (legal) way causes them more trouble than their serves cause me, because they can't improve their serves any further but I have a myriad of spin, speed and placement variations to confound them :).

Oh, and the pro's serves, where they start with their arm resting on the table are legal.  Their hand and the ball are both above the table and behind the end line.  All good.  If they toss the ball so it crosses the end line before being struck, it will be (fairly) obvious to the umpires.  Where they do take advantage of the rules is that the further away from their body their hand is to start with, the greater the distance toward themselves they can toss the ball, and I agree some are allowed to get away with a ridiculously obvious breach of the rules' intent in that regard.

Phew.  Rant over ...

I encountered a player who threw the ball up into the paddle creating a very high spinney short service.  It appeared to me that the ball did not even rise above the top of his paddle.  I believe the rules stipulate that the ball must be stroked when descending, or words to that effect.  In my opinion, that makes the serve illegal.  I tried to duplicate that serve in practice.  It took hours, but it is not in accordance with the service rules so why try.