I only adblock the companies that do pop-ups/pop-unders, or verbal ads. Flashblock tends to take care of the worse offenders anyway. If the ads are supporting a community then, I figure they deserve the change to appear, even if I'm probably not going to do anything with them.

Same thing with the PVR ... if it's an interesting looking commercial, I'll occasionally go back to watch it the first time I see it.

Of course, that might just be me.