Jackinthegreen
Explorer
I think this is a modest but nice illustration of different approaches.
If you're playing in the style advocated by Lewis Pulsipher, and by Gygax in his PHB and DMG, then if the players go to sell a magical sword without realising that it is magic that is their tough luck - part of the skill of play is identify magical items!
But in other approaches to the game, the GM will draw the players' attention to magical items that have been placed. At which point the idea of magic items as "rewards" starts to become less relevant - at a minimum they are no longer rewards for skilled play in the Gygaxian sense.
For instance, in my 4e game I simply point out the magical items to my players after they inspect them during a short rest (or sooner than that on a successful Arcana check). This is because, in this game, magic items aren't a reward; they're a component of PC-building.
Different games might fare better with different approaches like that. In terms of 3.5, I've noticed there are definitely some standard magic items that are heavily implied to be assumed and thus become "regular" gear, but there are also a few more circumstantial items that fit the bill for something so nicely that I can definitely see giving them out as rewards if not for "skilled play" then for going on a quest or otherwise putting a lot of effort and resources towards getting.
On the topic of some player-driven stuff versus a DM's "preconceived notions," I was once in a group playing a cleric with the Air domain. The party was captured and basically turned into gladiators and crap. During one of the matches there was magical fog in the arena. Naturally, I had my cleric use Control Winds to move the fog off. The DM got this look on his face that plainly said he not only hadn't foreseen this, but he was pissed off and didn't like how I had "ruined" the encounter. Even when I pointed out that, according to the rules on various fog spells, a strong or severe wind would disperse the fog in one round and since the Control Winds spell lasted for 10 minutes per level and didn't need me concentrating on it unless I wanted to change it, the fog should disperse and wouldn't be coming back for a while the DM was like "No, the fog comes back immediately."
That's what I'd call a preconceived notion. I suspect [MENTION=22779]Hussar[/MENTION] would have at least been irate at that point (if not before since us getting captured was indeed BS) and probably even walked off by then. Luckily I didn't have to bother with that table for much longer because they stopped inviting me. At the time I was a bit dismayed, but now I realize the DM was full of himself and I dislike being around people with that kind of outlook.