Ask HN: WebEx alternatives?

The company I work for (B2B publisher) currently publishes sponsored webinars using WebEx.

I'm sitting down today to rework some related code -- and it occurs to me that it is 2010, and I can't believe there are no viable competitors to WebEx (at least for larger presentations, e.g. over 100 people).

WebEx continues to be the same bloated, clunky, overpriced, enterprise-y service from 2003. How has no one yet found a way to compete?

If anyone has had positive success with another service for large scale events, I'd be so happy if you could share that here.

If not, hopefully one of you guys will get inspired to take on a dinosaur that, as far as I know, is continuing to rake in the cash.

EDIT: To be clear, I'm specifically curious about webinars as opposed to smaller meetings or presentations. The publisher I work for has produced webinars with over 1,000 participants so the need to scale is paramount. (That said, the need for every participant to be able to participate as in a traditional webinar is actually a bit unnecessary.)