Where does "good acquaintance" end and "real friendship" begin?

I've met loads of Mudcatters in real life and started attending several regular local (and not quite so local) sessions and singarounds as a result of Mudcatters' encouragement.

I even met Max on his great "UK Tour".

I've had people I'd not met in real life at that point do me big favours (one of note being Sylvia Needham's saving me tickets for Russ Barenberg's intimate pub back-room gig in Derbyshire the night after I'd seen him play the Festival Hall with the full Transatlantic Sessions mob, and making sure they were the best seats in the room...possibly because I was travelling 185 miles each way just for the gig).