The Decemberists - Nope, they're still going--you just wouldn't know it because people immediately quit talking about them after that big rock opera disaster they put out in 2009. I'm not sure what of the twee, wussy Pitchfork crowd from 2000-2010 are still putting out acclaimed work (I love Illinois but forgot to listen to most of the rest of Sufjan Stevens' work.)
Rilo Kiley - This band started in 1999 but I didn't know about them until about 2005 so I can't count them. Their breakup was very silent (and didn't matter much, Jenny Lewis and Blake Sennett have periodically reunited without the other two.)
The Strokes - extended hiatus, can't count them
The White Stripes - I wouldn't have known about them in 1998-99
The Vines - who?
The Hives - only know two of their songs
The New Pornographers - Can't count them because I wasn't paying attention in 2000.
Sigur Ros - they never broke up and I was paying attention in 1999, not 1997, and also I haven't heard anything they did since 2005
Gawd, this is hard!!!