But there's a bright/flip side to this, in that particularly big brands who approach the problem correctly could create some really good community. I'm thinking of the "maker" space in particular, where tool vendors could sponsor forums, events, etc that would be actually useful to their customers. (Mid-size b2b software vendors actually do a pretty good job here, with their webinars and such.)
Basically, it's the generalization of the sporting event sponsor: you sponsor that skate-boarding competition to inspire more kids to do skate boarding.
The problem of course is that it's hard to imagine the communities that would form around "canned tuna" or "sham wows". But then, I've never really understood those kinds of products, or why they'd even bother advertising. Is there really a difference between Crest and Colgate? Why would either of them bother advertising anywhere, let alone on the web?