Zynga games in domain name

I'm sure most of you know, but Zynga created games such as Farmville, Petville, etc..

Question is, is it possible to run into trouble for owning a domain like "mafiawarscheats.com"?

My point being, can we get in trouble for having the name of one of their games in our domain?

Yes you can

I've seen domains that have mafiawars in them, but not sure if its caused any issues.

You can get in trouble if you use trademarked names in domain names and you use that name to market their product or something like it. For example, I owned a domain with amex in the name that had backlink traffic of a couple 100 uniques a day. I setup a page that pushed credit card offers, which obviously had a very good conversion rate. I eventually got a letter and phone call from an American Express lawyer about it because I was capitalizing on their trademark.

There is a whole underground (kind of) movement around this that I'm not really invovled in because there is good money to be made before the wolves come knocking.