Trolls, fakers, and pervs are all different things. Though we have plenty of each here at LPSG.
A troll, as the definition you dredged up suggests, is someone who goes out "trolling for suckers." What this means is that they are assholes who, with nothing else better to do, enter into online conversations with the intent to rile people up and make people angry. They post offensive, controversial, or just plain stupid/ignorant crap that they may or may not believe, typically in as inflammatory a manner as possible, and then sit back and revel in the chaos they create. Typically they have little to no investment in the communities that they seek to disrupt, they simply show up and start spouting crap for no good reason. Of course, acting this way makes them obnoxious so the second definition fits as well which is why some people are confused.
There are some more devious more highly evolved trolls that don't follow this pattern of behavior to a t. These trolls may try to post reasonable things for a while to establish some credibility or make themselves seem sincere, then they'll slide in something inflammatory to get the desired effect. They may post things completely contradictory to each other, such as how much they love prostitutes and that they are going to visit the USA on a sex tour in one thread, and in another thread they'll start an argument that countries where prostitution is tolerated are inherently evil. Johnschlong is an example of this type of troll. Some other trolls operate with a more specific agenda. Science-denier trolls or political hack trolls like JQBlonde fall into this category. Their purpose isn't only to stir shit up, but also to get a particular abhorrent opinion across and force it into the general dialogue. Sometimes these trolls will actually adopt an opposite position to try and prove their point. Actually I guess Johnschlong falls into this category as well... since his agenda is to try and convince everyone that the USA is bad.
Fakers are completely different, though there is some crossover. Most fakers here are picture collectors. They pose as hot young girls or boys and then collect naked or penis pictures from everyone who's dumb enough to send them, or they trick people into jacking off on webcam for them because they get off on duping people into doing that or they haven't found their way to xtube yet. Some fakers adopt false personas because they are attention whores, or because they are dissatisfied with their lives and want to fantasy roleplay, or because they are dumb enough to try and trick people in to wanting to meet them (though they haven't quite thought through what's going to happen if they succeed).
Some fakers fake just to fuck with people. These are the ones that cross over into trollish behavior. People with multiple accounts that interact with each other or who create completely fabricated drama on the boards. Like the trolls, they think it's fun to trick and to provoke.
Then there are people who don't fall into any of the above categories but are simply obnoxious in their own right.