I thought I heard this news ages ago, but it was probably the last time he refused a big prize. Just shows being good at maths doesn't mean you have any sense about money.
Russian mathematician rejects $1 million prize

I just read this yesterday.
At the very least, he could donate down the line to whatever mathematical endeavor he is fond of.

well, just go to show how different a great mind think to that of majority of folks. It would be weird to come up with such a breakthrough, and then get money. I believe clever people don't think the way we do at all:) Anyhow, being able to think and imagine the way he does, money cant buy that. Just to know such a person, is an honor. It makes him rich, and such a person will always be looked at for giving answers, to things that puzzle others...it is a gift that he got. Perhaps he had already received his prize in life. Perhaps he just made us all wonder...But if someone don't want to accept a prize, you can give it to his wife, or child...give it to those that are closest to him, they would know what to do, with it:)

This is a most puzzling story. I assumed he was 100% devoted to mathematics, had no need of the money for sustaining himself and was not interested in other things he could do with the money. But the truth appears to be far stranger and sadder. Perelman is reported to have left his post and given up mathematics, with some sort of huge grudge against the mathematics community. There is little doubt he has some sort of mental disorder, maybe with a paranoid element.
To me this is highly reminiscent of Fischer, who acted similarly having his achieved his life's aim, with the difference that he had the sense to accept the sizeable prize money (half from the Icelandic Chess Federation, half from Jim Slater).
It's a great shame. For about 30 years I have been aware of the importance of the Poincare conjecture, and have great admiration for those involved in the solution of what is intrinsically far more important than Fermat's Last Theorem, possibly the most intrinsically important problem to have taken such a long time to solve.
It's only now I realise how up to date our teachers kept us when I was at Cambridge. I recall being excited to be told about the Thurston geometrisation conjecture (proved by Perelman) in about 1980 and its potential role in 3 dimensional topology, and in particular proving the Poincare conjecture. I am still in awe of Thurston for proposing the conjecture in the first place. It seems clear that Perelman is right to flag how importance Richard Hamilton's work was, which provided a grand plan which Perelman successfully implemented, and it seems the work of Shioya and Yamaguchi was vital for one key part of this proof.
For people who have not studied topology at university (yet) who want to get a flavour of what the conjecture is about, the wikipedia page on the solution looks a good introduction (better than the one on the conjecture).
Russian mathematician rejects $1 million prize
NEW YORK – He said nyet to $1 million.
Grigory Perelman, a reclusive Russian mathematics genius who made headlines earlier this year for not immediately embracing a lucrative math prize, has decided to decline the cash.
Perelman's decision was announced Thursday by the Clay Mathematics Institute in Cambridge, Mass., which had awarded Perelman its Millennium Prize.
The award honors his solving of the Poincare (pwan-kah-RAY) conjecture, which deals with shapes that exist in four or more dimensions.
Jim Carlson, institute president, said Perelman's decision was not a complete surprise, since he had declined some previous math prizes.
Carlson said Perelman had told him by telephone last week of his decision and gave no reason. But the Interfax news agency quoted Perelman as saying he believed the prize was unfair. Perelman told Interfax he considered his contribution to solving the Poincare conjecture no greater than that of Columbia University mathematician Richard Hamilton.
"To put it short, the main reason is my disagreement with the organized mathematical community," Perelman, 43, told Interfax. "I don't like their decisions, I consider them unjust."
Attempts by The Associated Press to reach Perelman, a resident of St. Petersburg, were unsuccessful.
Carlson said institute officials will meet this fall to decide what to do with the prize money. "We have some ideas in mind," he said. "We want to consider that carefully and make the best use possible of the money for the benefit of mathematics."