If Meetup were fundamentally limited, I'd have to agree. There's not much I want to do with the site that is limited by sponsorship status, though. You can join unlimited "groups", you can vote, RSVP, even suggest new groups, all free. I think the only things you have to pay for are the right to override venue selection and set worldwide agendas.
It'd be nice if those features were free too, but I think it's a useful site overall. It sorely lacks membership in some areas. More than half the groups for which I'm signed up have too few people (in Portland) to even merit a meeting.