MyBB Community Forums

I'd leave it the way it is (guests can view/lurk).
The thing is, everyone's different with signing up with sites. No one's in the same mood - you know that mood where you're really lazy and signing up seems like a hassle?

I kept my forum open to guests since launch, every now and then I see intro. threads that say they were long time lurkers but decided to sign up now. No, this won't mean every single lurker will sign up for your site, but I believe a majority will.

Besides, a member with 0 posts really doesn't help anyone either.

What Richard said is so true.

The very first forum I went onto, I lurked for 8 months before signing up.
It didn't feel safe/right to me, so I just kept browsing until I finally felt comfortable enough to do so.

We've already had a few of those type members, you get them on most forums. Quite a few have decided to sign up after being lurkers for a short period. However with mine it's basically double on days like Monday, so my concern was limiting guests on that specific time (an hour before RAW restricting it, hour after it allowing it) could harm SEO. Like you said, a member with 0 posts helps no one but it means that member now gets the promotion emails sent out and has the option to return and get involved easily.

But you're right - I'll rely on the quality of the content to encourage the guests to get involved with the discussions. Wouldn't want to risk harm to our main traffic source (search engines) for a few extra sign ups. Thanks.