I got a couple of job offers from people who knew me through my online activities.

My online interaction with the Singularity Institute led to my collaboration with them.

I was introduced to a potential customer by someone I contacted, whom I knew only through their online presence.

For Singularity Summit 2012, I got some generous couchsurfing offers and ended up staying at Vassar's place.

(There was some minimum F2F time for some of the above, but everything got started online, and the great majority of interaction was not F2F.)