Not really. I just haven't bought any Activision games because all they seem to want to put out is Call of Duty and Guitar Hero (not so much the second anymore). I am looking forward to getting my hands on Prototype 2 next year, though.
Now, publishers I do boycott? Ubisoft and Square Enix, because while both of them might get a game out worth playing every now and then, most of the time it's more and more crap from the two of them. Well, with Ubisoft it's more mediocre stuff and Square Enix is the pusher of flat-out garbage. But still, neither company's games are usually worth my money when games are as pricey as they are and playing time is not infinite. Plus there's just about nothing I'd miss if either company went under, either. A world without a jillion Rayman ports, Final Fantasies out the wazoo, Tomb Raider, and Kane and Lynch? Sign me the fuck up please!
I'd probably be boycotting EA for all their shitty PC DRM too, but it has to be on a game by game basis because sadly, they actually got their name on some stuff that's too good for me to pass up (top of the list would be Mass Effect).