That is a two-year yield of 4400% vs. USD (from 0.3 USD/BTC to 13.4 USD/BTC). In gold terms, bitcoin is also doing well.
1) Bitcoin has in November reached block 210.000.
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2) The "bitcoin economy" finally started to gain serious traction 2012.
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3) Attention from big players.
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4) The bitcoin business space has also started to attract venture capital in 2012.
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5) Many, many more developments in 2012. Partial list:
Bitcoin magazine started shipping;
Launch of The Bitcoin Foundation;
Blockchain.info launched an excellent hybrid ewallet service;
The Bitcoin conference in London was a success;
The birth of provably fair gambling and Satoshidice, Bitzino and others;
bitcoin-2-email service Coinapult;
in-game item exchange is rising;
Explosive growth in the bitcoin reddit forum; ...
Full article: http://seekingalpha.com/instablog/530678-minorman/1409731-best-currency-in-2012