Yes, true, as Jay said at BlizzCon we are planning to have some amount of items that will bind to a character upon equipping them.
We absolutely won't have items that bind when picked up, except for the obvious things like quest items and other character-specific items that wouldn't/shouldn't be tradable anyway.
That alone, I think, should dissuade the most severe concerns with binding items. And before I go on just understand that while a lot of this is very stable in its concepts, the details aren't final.
For Bind on Equip (BoE), the idea right now is that it would only be applied to "end game" items of specific quality levels. So to start, it's not every item, and it's not even every item above a certain level. For the BoE items that will exist, you can pick them up, if you don't want it you can still trade it, or give it to another character, a friend, vendor it, whatever you like. But, if you make the commitment to keeping the item and equipping it, yes, it's yours now.
The reasoning is that in reality we need a solid way to keep the economy stable at the end game. With items building up over a potentially infinite amount of time there's no way to have any measure of control over worth of items. While an item may be the rarest and best in the game, over four or five years a stockpile has built up and those items are now commonplace and hold little value as compared to their rarity. The gold being earned by players stays the same or likely increases as players become more proficient at playing the game while they spend less as items lose their value. Gold value drops, and we're skirting into a familiar cycle.
By ensuring we can rely on some amount of "consumption" of items, their relative worth stays high, the market is predictable and both sellers and buyers enjoy a stable marketplace for (hopefully) many years.
Diablo II has an inconsistent approach which is the somewhat stable Ladder economy, since it's quite literally flushed out every so often. But it's a very intrusive approach to a problem that could be solved through other means that don't require making everyone start over.
As a quasi-aside: There's an idea being thrown around, and this is really not guaranteed in any way, that some or potentially all items that are bound to you could be bound to your entire account. So if you yourself "own" an item from it being bound, you can trade it between all the characters on your account freely. Feed alts your old-but-still-very-nice items, etc. That's just an idea, it may not take shape, but it's a possibility. One obvious issue with it is that it removes market demand. If you already have the best staff in the game you'll never need one again, eventually no one ever needs them, prices drop, etc. etc. That's maybe an over simplified scenario, but anyway, we'll see.
