Nope! I fitted some old X-Lite Stubby bar ends to my 700c-wheeled commuter last year but removed them a few months later; only really any good IMO when you're spending all day on the bike. :)
As above. Who cares sop long as you like them. I use them as I like to be able to change positions and like XC says it allows me to flip the bike over and I have a stand that means my GPS is safe.
I use them on a norco with a riser bar. Good for climbs as it allows me to put my weight further foward as well as hooking the back wheel in for traction. They also can take out some wankers wing mirror without me breaking my fingers plus a damn good place to hang my helmet.
I've got cheap ones on my risers, looks fine and who cares, makes sure they've got a curved in bit so they deflect of trees rather than grabbing. Like Mikes pic.
Will not ride without them, tried for abit hated it.