I've been posting here for a very short time. However, I have been coming to this site, reading the blogs and theory pages, for quite some time. Here is an observation that I've made.
There are essentially 3 types of people, exceptions do exist, who post theories about Lost on this site.
1) The Fact Checker - This person is well versed in the details of the show, and, if they don't immediately know certain facts, they take the time and effort to research them thoroughly. They can quite clearly state the meaning of the show's past and current events but rarely, if ever, hypothosize or make statements that contain a 'What if?'. People can easily be put off by a Fact Checker as either the person they are correcting is overly sensitive, refuses to except the facts, or the Fact Checker, themselves, makes statements in an 'I can't believe you think that' condensending sort of way.
2) The Postulate(r) - Thinking that they are more versed in the show's facts than they really actually are, this person can't help but shout out each and every theory that they've given a day's thought to. Initially based on facts, these theories tend to be filled with 'What ifs', 'Why couldn'ts', and assumptions that no events in the show actually support. The Fact Checker is quick to debunk many of these theories, yet, a good Postulate(r) will try to take what they have to say and make their theory stronger. This, however, almost never happens.
3) The Dreamer - Unlike the Postulate(r), the Dreamer doesn't actually command any knowledge what-so-ever of the show's facts. Their theories completely ignore any and all established events, facts, or rules and bring into question whether they are understanding, or for that matter even watching the same show as everyone else. They respond to other's theories with 'That's stupid', or 'You're stupid', and never have any facts to back up their unintelligible statements. Both the Fact Checker and the Postulate(r) are quick to respond to the Dreamer which sometimes ends with more 'stupids', slamming of doors, and a few 'you're not my friend anymore's'.
Don't think for a moment that I'm not aware that I fit into one of these molds myself. ;)