Trolls vs Liars

Serious question (posting on a couple fora): what's the difference between a troll, and a plain liar, on the internet these days?  Is someone claiming to be a sociology student conducting a study, when he's clearly not familiar with basic terms used in such studies, a troll or a liar or both?  (IE, he thinks being asked about his interview schedule means giving away confidential information about the interviewees, when it really means what questions has he included on his script for conducting the interviews) 

Hmm... Trolls vs Liars.  That sounds like a more interesting movie than Aliens vs Predators 2... ;-)

Edited to add Context: #25.18