I've always had the idea in my mind (and a former GM reinforced this between wizards and sorcerers) that a notable number of wizards look down on sorcerers for not being academically trained in their magic.
Now when I look at the fluff behind Pathfinder sorcerers (never played 3E) it seems that they could be just as snooty towards wizards for the wizards having to "learn their magic from books".
Then when you throw witches into the equation their powers are basically granted to them by some mysterious force which makes it seem like both of the other classes could look on them with disdain.
I'm basically asking your opinions on this matter and how you play your character/NPC spellcasters. I'm not saying <i> every </i> wizard has to fit the "no like sorcerers" persona.
Also, while writing this post this question came into my mind: Do wizards have to have some special quality to actually train to become a wizard, or could anybody with the privilege of having the cash and being in the right neighborhood become a wizard? (i.e. Could Valeros have been a wizard had he had access to a school?)