Motivation for guests to register. Continue as a <username>

[wegorz23]

I saw on one of sites that I use something like that:

I was not logged in on this site, but it automatically taken my fb name and show it to me. Its good option and I want to use it on my forum to motivate guests to login/register via faceebok. It is possible to make it with IPS now somehow?

 

And another thing is motivate somehow guests to register. One day we had error on forum (sth with cache) and site was displayed only for registered users. On this day we had record with new registrations. We don't want to disable visibility for guests, but motivate them to register. We have enabled option for guest to join the discussion (and register later), but still have maaaaany guests (over 700+ right now) on site, that will never register. My idea is to show them for example only 2-3 pages from topic, and when they read it longer show them popup with registration. It is possible with IPS or some plugins?

What else ideas do you have to engage/motivate users?

[wegorz23]

I found sth like this:

I will test it.