Hi Martin:
Do you have a youtube of the 1st incident you mention? The second is the "cantu vs. the russian" incident, widely available on the net....
For me, it all comes down to whether a house uses a forward motion rule or a chips released rule. Under forward motion, then, yes pushing a stack "past the line" is a bet. Under the chips released standard, however, the bettor has to take his hand off the stack and the chips have to "hit the surface of the table".
Personally I like chips released because in the States 99.9% of tables don't have betting lines, so if you're trying to enforce forward motion on a table without a line, you have to parse every motion and see if it meets your standard of being past an imaginary line or plane. One judge may think the chips are sufficiently far forward while another may think they haven't crossed the imaginary plane... also the same judge may rule it binding from one angle, whereas they might rule it non-binding from another angle... With chips released the player's hands are either on the stack or they aren't, so it's clear from any angle and every judge rules the same, they're either released or they aren't. That's why alot of houses in the States have gotten away from forward motion and gone to chips released....
You can still strongly warn or penalize a player if they abuse chips release of course. You can also as TD make a determination that even though it's a chips release standard, that "if it looks like a bet, it is a bet" and use TDA 30 "player must make his intentions clear".
The downside of chips released is that you will have these outlier situations like the Brandon Cantu incident you mention as your 2nd example. I agreed with Jack Effel's ruling at the time given that it was my understanding that the chips release standard was in effect in that circumstance. But I understand it was very controversial and alot of people felt the Russian player had "gone over the line" (no pun intended) even if chips released was the de facto standard in effect. I would add one other incident that I think fits this controversy... that was a play at the WSOP by Mike Matusow several years ago where he did a "hail mary" and extended his arm with a fistfull of chips then pulled it back and it was ruled no bet because he didn't release the chips, anyone have a tape of that? Thanks for bringing up the topic, another possible issue for the next Summit, IMO.