I agree, but how does Google leverage their existing products and promote collaboration with presentation software? Google Calendar worked because planning and sharing events/meetings makes sense to be integrated with GMail.

As I've said before, I think this is going to be a different story because, while collaboration brings a lot of value to presentation software users, I can't see a killer app that Google can leverage beyond Image Search that would make their product a must-have. Zenter has done a great job making a connected presentation app with a very slick Google Search-based image import tool.

Pound for pound, I think Zenter has a fighting chance as long as it keeps innovating on the feature front. Don't forget that collaborative presentations will likely give rise to a slide sharing community (i.e. slideshare.net), so there's more to online presentation software than the app itself.