Unless I am mistaken, the Rogue is balanced on the presumption he gains Sneak Attack about half the time? That is, Quarry/Sneak/Curse aside, the three Striker classes are meant to be balanced?
(Of course, it could well be that the truth is somewhat different, say "the Warlock must gain Curse bonus damage 2/3 of the time or he falls behind" or "the Rogue don't need Sneak bonus damage more than 1/3 the time or he becomes a bit too good" or whatever.
My point is for the Rogue it can't be enough to simply use the rules and expect class balance. Instead, the Rogue is a bit like the 3E Ranger, whose power depended a good deal on whether you used his favored enemy monsters or not.
That is, our conclusions regarding Stealth should be governed not simply by bickering about the RAW and discussing corner cases. No, we should aim to arrive at a situation where the Rogue gets to use Sneak damage as much as is balanced.
There is no right or wrong here. A DM with a new player, or with a player not interested in minmaxing, could well hand out Sneak Attacks to all the Rogue's attacks, and it would still not be overpowered, or encroach on the other PC's fun. A DM with a player good at talking his way, could restrict Sneak Attack to only the bare minimum allowed by pure mechanical considerations: flanking, powers, and just possibly a single bonus use from skills.