I think it's all in your perception. Are you using protection? Are you very clear with them that this is a one-night stand and that you don't want a relationship?

Besides the obvious worry of STDs with multiple partners......I don't really see the harm.

That said - are you doing this as a coping mechanism? It's hard to find a line when you start using sex to fill a gap in your life. If you just genuinely like it and aren't using it for that....then go right ahead. But, if you think of this as affirmation from partners or filling some kind of void from your previous relationship....then I would think twice. It doesn't take long before a situation like what I just described turns into a kind of sex addiction.