Underwood Dudley published a book called [mathematical cranks](http://rads.stackoverflow.com/amzn/click/0883855070) that talks about faux proofs throughout history. While it seems to be mostly for entertainment than anything else, I feel it has become more relevant in modern mathematics. Especially with the advent of arXiv, you can obtain research papers before they are peer reviewed by a journal. So how does one tell between a crank proof and a genuine proof? This seems to be [tough to discern in general](https://mathoverflow.net/questions/6912/6916#6916). 

For instance Perelman's proof was not submitted to any journal but published online. How did professional mathematicians discern that it was a genuine proof? 

So how does one spot a [crank proof](http://en.wikipedia.org/wiki/Crank_%28person%29)? It seems that John Baez [once (humorously) proposed a "crackpot checklist"](http://math.ucr.edu/home/baez/crackpot.html). Would this seem like a fair criterion?