I have been researching these cloud mining services and honestly I found so many different opinions. CHecked several reviews... Checked the cloud mining services' websites, and threads here on the forum. My finding is that PBmining is among the best, however, I found many bad opinions too, and there is another company, Genesis Mining, which seems more trustworthy to me. The got excellent ranking on www.cloudmining.guru, I found this a couple of days ago: http://cryptomining-blog.com/2706-trying-out-the-genesis-mining-scrypt-cloud-mining-service/
and they explain all concerns you guys are contemplating about here on their website FAQ.

A scammer accused them of not being legit, not having a farm, etc. and their reply was super cool and funny. Look at this!
https://bitcointalk.org/index.php?topic=467587.0;all
just scroll down and read the scammers posts and then the company's reply... Priceless