What determines swing speed in an individual?

Independent of form, how much of swing speed is strength, and how much is other natural factors like types of muscle fibers etc.  For example, in baseball strength has little to do with how fast you can throw a ball.  A pitcher might not have much strength at all, but still throws fast.  Does someone who can swing a bat fast or throw a ball fast have a faster golf swing, if they have the same form?

Swing speed requires mostly fast twitch muscles. Obviously, you need to have muscle in the first place to hit it, but lifting too heavy of weights can actually hinder your swing and thus the speed you can generate. If you're looking at lifting weights I would recommend a program  with lighter overall weights, but more reps and flexibility exercises. Someone who can hit homerun after homerun might not generate a lot of clubhead speed, just because a baseball bat is much heavier than a golf club (wooden ones, anyways) and require more brute strength. Really, it all comes down to technique. The further you can get the club to lag behind your hands, the faster your club will go as you whip it through impact. This does, however, require the strength and flexibility to be able to coil and uncoil more than any other one motion. Look at Rory McIlroy as an example: He is 5'10", and still generates 120 mph of clubhead speed. It's because his hips uncoil almost twice as fast as an average golfer, not because he has amazing strength. In fact, his hips uncoil fast enough that somewhere after impact, if you watch very high speed tapes, you will see his hips stop and actually REVERSE direction, in almost a recoil fashion, for only a few frames. That reverse is almost as fast as the average golfer comes around forward, and shows just how fast his hips are moving. They have to come back because of how the muscles connect, just so he avoids tearing them. That is an almost perfect example (in my opinion, at least) of how lagging the hands behind the club and the club behind the hands will create additional swing speed and longer drives.

Very informative post.  So now I'm wondering if it can be broken down in percentages between form, strength, types of muscle fibers, flexibility, coil/uncoil, etc.....I has to have been studied?

Yes, that sounds like something that would be very helpful, perhaps adding tips on how to spot a deficiency of any one piece by looking at a swing video so you know how you can improve your swing. Don't get me wrong, I'm not thinking it's all about distance, but a little extra distance off the tee without sacrificing accuracy is always helpful.