Short URLs in trouble

Popular URL shortening site Trim is going to close by the end of the year, due to financial strain. URL shortening was especially popular on Twitter, where every character was at a premium, due to the 140 character limit. I never really understood how these shortening sites made any money, especially with the glut of bandwidth being sapped up by Twitter and other similar sites. The closing of Trim, one of the more popular sites, would create a strange situation for users - where many URLs on posts would essentially point to nothing. However, Trim and many other shortening sites have signed up for a URL redirecting service, 301Works, which has not yet launched. One wonders though - what happens if 301Works goes belly up (it's not even technically up)? I myself have frequently used URL shortening without much second thought, but this situation has reminded me of the complete fragility of most weblinks.