I've seen it with Desktop tower defense. Can't tell I appreciate it, but it should help fighting theft.
Though, is it really that hard to crack? (wrt to code obfuscation) Any experience from flash developers?
Calls to the standard library and globals (like mouseX), etc. will remain as is. So my guess is that it would be not too hard to alter. But I'd be surprised if such simple measures wouldn't cut off the majority of leechers. Though as soon as one cracked version shows up on the internet, the whole maneuver is rendered futile.
This is indeed an interesting topic, especially considering the options a) run everywhere and show my ads (mochiads, cpmstar, ...?) or b) run only at my site so I get all the traffic (not sure if this is compatible with those ad-servers).
Well... this reminds me of the drm-struggle. Although the negative impact for the enduser is a lot smaller (dysfunctional swf on a leecher site?), you'd have to ask yourself how much time you'd like to spend with the arms race rather than implementing features, fixing bugs or writing new games. As a "content provider" there is probably no other way to keep sanity other than accepting theft to some degree.