It's certainly regional and probably differs down to friendship groups.
very fair - my apologies :)
"Bimmer" usually refers to cars while "Beamer" refers to bikes. At least that's the general consensus on the forums.
I think the distinction has lost any meaning outside of the most ardent fans. In the west there are few BMW motorcycles and so Beamer generally applies to both.
'Bimmer' I was aware of too, I didn't realise there was a distinction between the cars and bikes, I always assumed it was just regional differences!
"Beemer" for bikes and "bimmer" for cars is certainly what I have observed among BMW enthusiasts. At least on the US west coast.