This a good post and I've touched on this subject before. The motives to being one way on here and different in person vary from person to person. Anybody that has met me in person or spent any length of time will tell you I am the same in person as I am on the board. That goes for one on one or while in a group of people.
As for being a jerk on here and sweet in person..... That's not that hard to understand is it. If they are jerks in person then you are gonna tell them to hit the road jack and then they won't get to the promise land
Also how many true "jerks" actually tell you their board handles when you meet them. If they use other avenues for you to screen them with so that you never know their board personality then IMO they are cowards with no backbone to be who they say they are.
If they do tell you who they are then I think that says a lot about them as a person. They are who they are irregardless of what people think. That's a good thing. There is also a difference in being honest (sometimes brutally honest comes across as being a jerk) and being an ass.