Bandcamp does limit the number of times you can stream something. I was streaming a Mick Chillage album last week; this week I tried to listen again, but I got a pop-up telling me to open my wallet. I clicked "no thanks"; now when I hit play, the same pop-up window appears, and I can't stream it anymore.
They just started offering that in the last week or so. I think the number of times one can listen to an album are up to the person who puts it up on BC. So the down side is no more endless listens to a particular album, of course if you listen to said album several times then you probably should do the right thing and support the person. The upside is maybe labels like Projekt might start offering entire albums for preview.