1) Due to a cash crunch, they sold off their flagship mine last year (the ocampo mines and various projects) so the market is (correctly) assuming that the company is willing to sell other mines. Other miners have shown commitment to the business of mining. Thanks to the myopia of investors, the market rewards companies that realize cash for their assets sooner rather than those that try to grow their business.
2) They did a buyback at the beginning of the year, so stock price held firm while others were crushed in the last few months of 2012. It also reduced the short availability (for months, it was not possible to short AUQ). It still hasn't corrected for that outperformance.
2) They aggressively boosted production estimates for 2013 (while other miners have been giving more realistic estimates). It should make the next earnings release more interesting.
4) Many financial blogs and sources have been pumping the stock. Fred Hickey in Barrons gave a really aggressive production estimate (the first of which the company already missed).
The market cap is governed by the current share price. If the forces are skewed in favor of pumping the stock, then of course the market cap will be inflated. IMHO it's a big short here (paired with a long in GDX or other miners)