1. Will it be hard for a laid back northerner to meet new people in Boracay?
Well, I think that entirely depends on you. As for the crowd in Boracay, you generally have a lot of young people looking to party. If you're sociable enough, I don't think you'll have a hard time making new friends in that environment.
2. Will I get bored if I stay for to long, say more than 2 weeks?
Again, that depends on you. I know I will be bored staying that long in Boracay. But then again I look forward to doing activities when I'm there - swimming, snorkeling, sailing, etc. Two weeks is really long for me just for that. But if you're there for the crowd and the parties as well as the activities, 2 weeks may be OK.
3. What nationalities travel to Boracay? Mostly Americans?
You get a handful of Americans, but as a percentage of the total, they're pretty small. You get a lot of Russians, Germans, Japanese and Koreans (especially Koreans). I also notice there's usually a higher concentration of Europeans in Boracay during winter in Europe.
4. Planing on going in January. Is it high or low season and how is the weather?
January 1 is peak of the peak because of the New Year celebrations (fireworks and all). After that, the crowds start to dwindle and you're left with a much thinned-out crowd. The island won't be deserted or anything, just not crowded, which for me is terrific. So yeah, that would more or less be the low season.
Weather - January is not the rainy season, so that means a lot of sunny days by the beach. The nights here are also relatively cooler (by Filipino standards, at least) until February.