A lot of these companies are sadly just operating ponzis under the guise of cloudmining, so you've got to do your research. If they can't provide sufficient evidence of mining hardware then they're a scam. You could still make money from them but remember they can go bust or scam you at any time.
There's a whole list here or legit and scammy cloud mining companies with people posting information about it:
https://bitcointalk.org/index.php?topic=739510.0For what it's worth, I'm buying hashing with Genesis Cloud Mining and I haven't had any problems with them.
How much do you pay and how much money do you make back? Ws wondering if it's worth it for me.