Personally, I'd have no problem if Chipmixer decided to require avatar space for their campaign--it's not that big a deal to me.  What I'm wondering is why it's seemingly a big deal for OP since he went through the trouble of starting up a thread about it.

Are there actually avatar campaigns that only pay for avatar space?  I'd love to be even more of a whore than I already am and rent out every pixel of advertising space I've got (that's a LOL). 

I don't know if that's true or not, but my guess is they're seeing a return on their advertising dollars since the campaign has gone on for so long.  I doubt they'd still be running the campaign if they weren't seeing results.