[vertex-four]

VAC streams the DLLs from their server at runtime, so they never actually sit on the disk. There's also a number of DLLs which are loaded and unloaded as necessary, to make it harder for attackers to dump the whole thing. I suspect that there are blackhat forums where people have discussed how to dump parts of VAC.

[bestdayever]

Generally any VAC update is met with a full dump fairly quickly on most sites.

[brownbat]

Cheating seems to involve more effort than just playing, getting better at the game.

[StavrosK]

Reverse engineering is usually more interesting than the game.