Couldn't a TAS theoretically be made to be proofed against slight desync? e.g. making jumps and manuvers that have leeway either way to account for slight amounts of lag, and every so often adjusting itself using cues from the game or whatever else.
Flash has random numbers and games are liberal about using it. There is also the issue of lag. Flash is quite good at managing lag on its own, but it is not free of desync risks due to random lag. And then there is the simple matter that there is no savestate support.
Flash games will most likely not be tasable in the close future.
you could fix desync by using these commands
PixelGetColor Retrieves the color of the pixel at the specified x,y coordinates.
PixelSearch Searches a region of the screen for a pixel of the specified color.
these can be used to check if a level has loaded, or if the character on the screen has reached a certain point on the screen
A similar concept is already in use elsewhere. Some RuneScape (a popular MMORPG) players automate their in-game tasks with a "smart" macro called SCAR. The program tries to recognize in-game objects by detecting patterns on the screen. It then uses a script to determine where to click next.
The RuneScape policies actually prohibit the use of bots and macros, but such a program could be useful in other browser-based games. The only problem is that the run time probably won't be the same on every computer.
There's a difference between a bot that needs to be roughly accurate, and a bot that needs to be utterly accurate (do everything as fast and as perfect as possible)
I once did a part of a game with macro's, it used pixel-color detection against desync. It's more like a lot of checkpoints than a frame-perfect sync.
But it worked smoothly. :)