Do black holes really exist?

Phil Plait wrote the best explanation of a black hole yet. (Yeah I know, even the name sucks).

He comments on a paper from Case Western Reserve University (PDF), that poises an interesting theoretical question, on how do they even form?

Einstein showed that as gravity increases, your clock runs slower. Literally, if you have two people, one guy up high above a black hole, and another guy close in, the guy outside sees the close-in guy’s clock running slower. Literally, time flows more slowly near an object with gravity, and the stronger the gravity the slower time flows relative to an outside observer. For a black hole, time literally stretches to infinity at the event horizon. Clocks stop. Update: Well, I was being glib. Actually they continue to slow, ever approaching stopping but never actually reaching it. I was trying to simplify, but oversimplified — I make similar comments below in this entry, so where you read that things stop, think of it as "slowing almost to but never quite reaching zero".

He explains it more detail in his article, that is a must read (and much easier to comprehend that the scientific paper indicated above.

ARS Technica weighs in on the issue too.