If a seller has a reserve, and the reserve has 
not yet been met (but there are bids on the item) 
can they just pull the item at any time?

I have had this happen a couple times, none of 
which broke my heart or anything (else I would 
have bid over the reserve or used buy-it-now)...

And if this is ok, how many of you sellers do 
this?  (And why, usually?)