Are chinese lanterns dangerous?

I was thinking of buying some for my birthday party and had a look at a few on ebay last night. Then it was weird because the news was on and a few stories went by then one came up about chinese lanterns! - what a strange coinkidink... the bbc said they might be a bit dangerous or something. I think it might of just been one of those weird coincidences that freak you out but I thought it might of been a sign telling me not to buy them. I don't know much about them and just how high the risks are so if you know a little more, or have used them please enlighten me. Thank you very much