One notable point is that one mining company, Asicminer, has a bitcoin-denominated stock that dramatically increased in value over the last several months.
It IPOed at 0.1 btc per share, now trading at about 2.5 btc.
Along with the increase in the value of btc relative to the US dollar, Asicminer now has a market cap (on paper) of about $125 million, from an IPO that raised about $200k.
They're based in China, Shenzhen I believe, and have been making the most of their self-designed asics. They currently represent about 18% of the entire bitcoin network, as measured by hashrate.