[bishnu]

You can invite non-G+ users to G+ events, I am not sure how smooth that experience for them though.

[wtvanhest]

It seems like they have to create an account. I just think they could definitely grab a user base that way. It wouldn't be the panacea, but they should be attacking parts of facebook now, not the whole thing.

[icebraining]

They seem to be working on it: http://www.google.com/patents/US20120079023