I've had different reactions from the players who use magic, and from people who either play there, or who used to play there, and I'm narrowing down my ideas about sorcery in the setting, trying to decide how to lay things out. I'm not finished yet -- I'm still waffling on 'the source' for the different styles, but this is what I've come up with so far:
My preferred take:
1) Most forms of magic require the would-be sorcerer to make pacts with other things. Either these pacts were made a long time ago, and you're just using what has been laid out (djinn-based magic and hermetic-style magic), or you're having to go on a spirit quest to encounter the 'things' which give sorcery of certain types (shadow magic, necromancer), or you need to sit around and let the spirits come to you so you can make agreements with them (totemic shape-shifting and shamanism). There's a very few exceptions to the rule, but most styles of magic use this form.
2) Magic involves knowing 'loopholes' in reality, and exploiting them. You're not beholden to anyone, you simply rely on your own knowledge and abilities to create spells and use magic. A few styles grant you the ability to communicate with certain forces, and you can command them, but this is more you pitting your will against theirs rather than any sort of 'agreement' made between you and them (unless you're offering them something in return for their aid to 'sweeten the pot'.) Powerful mages are walking incarnations of the type of magic they use.
The thing is, option #1 allows for more texture. Magic isn't just something people do, there's a weight to it -- superstition and such play into magic a heck of a lot more, and there's the 'otherness' associated with it. The game master has a reasonably good idea of what the mages are getting into when they use magic, but the players (and the mages most certainly) probably don't. What are the forces these guys are dealing with? What are the goals of those forces? Why are they giving you this power, and to what ends? And the stronger you become, the more power you use, the more you're drawing the attention of these forces to the world and what's in it. Is this a good thing? My end goal is that the most powerful mages can use world-rocking spells -- but would really, really rather not, for fear of what could come of such later. They use their spells carefully, tactfully, with an eye on the consequences.
Option #2 takes a lot of the superstition away. Sure, mages can have traditions and mythology to their magic, but the fact is, everything they do, they're aware of. Sure, some of the places their magic comes from is weird and creepy, but they have better control of what's going on. There's no 'otherworldly force' peeking in on them, they're not beholden to anyone, and as such as they get more powerful, there's less and less holding them back.
As a friend once asked -- 'what prevents powerful magicians from just blowing up or wiping out anything that stands in their way?' I've thought about this off and on since that question got asked -- hell, look at Dungeons and Dragons, and think about high-end magic users. What problem can't they solve with 7th to 9th level spells? Our general agreement was 'mutually assured destruction'. If you're whipping off the uber spells, you're risking your enemies doing so as well. Of course, this almost never stops PCs from doing it, so that 'agreement' is an illusion. The only reason mages aren't nuking entire cities and countrysides is GM fiat.
I'm more inclined to build in a consequence that people will become aware of over time. I want mages, regardless of how powerful they are, to have an awareness that the spells they cast now, will have consequences down the line that they just might not like. I want their benefactors to be something that they will not overcome, that they'll not understand, and that they may not want looking over their shoulder when they go about their business.
An example I tossed into the discussion: A powerful mage throws down a spell to erase his enemy from the earth. Time stops, and he hears a whisper of the shadow entities which grants him his magic. They're wonder who this target is, that he wishes to have erased. They wonder what made the target so important that he petitioned them to remove the poor soul from existence. Nobody else sees or hears anything, but the mage now has a private audience with some rather unearthly forces. And if his answers intrigue them enough -- sure enough, his target is gone. The entities have decided to claim the target for study, wondering about who the target is / was, and perhaps even dropping the target back into the world later, just to see what the mage will do next time.
Is there a point to all of this? Well, mostly, I'm just mulling it over in my head, and I work better when I've had a chance to write things out. Also, I'm curious what people think, and what their preferred way of looking at magic is. (Not 'by setting', just 'overall' preference)