Hbriem, I see what your saying but players like Scott Henderson use pentatonic modal playing all the time. I guess it just depends on how you visualize the notes on the fretboard.
Fleeeeaa, B minor and D major as you know are the same notes. What implies the mode is the chord progression underneath.
The B minor pentatonic could therefore also be seen as some of the notes used in let's say, A dorian, and they would sound like that over an A Dorian chord progression like A minor, G, D, Eminor A minor. However, play that same scale over a chord progression that is definitely B minor, then the scale would sound like a B minor scale etc.
Some useful tricks for getting a modal sound can be found using pentatonics, e.g. Play the pentatonic shape two frets up from your root (in a minor key), and you can get a Dorian type sound etc but you have to still be careful in your notes selection. It is far better not to learn it this way, although it was how I was introduced to it.
Also, in terms of how pentatonics are formed, I always thought that they just removed the weakest or less commonly used notes from the seven note scale, to make a scale that seems to be full of the stronger notes.
I might be wrong in all of this, I'm sure note boat will give a far better answer.
"I like to play that guitar. I have to stare at it while I'm playing it because I'm not very good at playing it."
Noel Gallagher (who took the words right out of my mouth)