I just about never actually abandon a project - but I put 'em on the back burner quite often, until I get my inspiration back.
(Only time I can think of that I actually abandoned a project was when I was planning a cool little action-adventure game that I had a story outline all worked out for - and then I discovered that Daniel Remar's Iji had already scooped me on every single thing I wanted to do with that, and did it better. Even then, I'd still like to take a crack at the gameplay concepts...I just need a completely different plot.)
