While I always advise caution for anything online, I know that while it wasn't a Dom/sub relationship (especially as I turned out to be even less of a switch I thought I could be, so making us two 'alphas') - though I opened up about my sexuality like with no one else before - I met my fiancé online, and we only met in real life about a year after having been 'together'. I had had bad experiences offline and online before, but he was different in a very good way.

I think that as long as there is communication and caution, things can transition from online to real life very well if the person involved is the right one.