I find parasites offensive as well. Many definitions of parasite specifically cite people as the object being described.

http://dictionary.reference.com/browse/parasite

a person who receives support, advantage, or the like, from another or others without giving any useful or proper return, as one who lives on the hospitality of others.

(in ancient Greece) a person who received free meals in return for amusing or impudent conversation, flattering remarks, etc.

Perhaps you are right as the definition of parasite in regards to people generally indicates living off others by their consent. Rather than living off others by threat or use of force.

I assume you are deliberately misunderstanding what I found offensive?

"Parasite" may be an unkind word for them, but there are certainly people who produce nothing but expect to be kept in a high standard of living at the expense of those who are productive. This arrangement is not sustainable, despite people thinking that California somehow has a monopoly on tech startups.

> what kind of net benefit to society do you think Zynga produces?

Zynga produces entertainment.

Well that is the gross benefit..