We are all quite familiar with the major Bitcoin exchanges; Mt.Gox, BTC-e, Intersango, VirWox, etc. For people looking for a more direct method of buying and selling Bitcoins, there are limited options, including bitcoin-otc, which can be very intimidating to the average person, and the Bitcointalk.org marketplace forum, an arguably risky place to trade Bitcoins.
Though the major exchanges support trade in nearly 20 different currencies, that represents less than 15% of the currencies being used worldwide, thus keeping Bitcoin out of the hands of the people who probably need it the most.
I don't know how many times I've heard the question asked, "can I buy Bitcoins with PayPal?" While yes, you could, unfortunately no one is going to sell you Bitcoins for PayPal unless you have developed a traceable and positive reputation in the community. Now, with Bitcoinary, it's very easy to do so.
Bitcoinary takes the credibility system from bitcoin-otc and gives it a web-based front-end with a facility for private messaging. People can now trade Bitcoin and build a history, all on one user-friendly site.
Solving the chicken-and-egg problem, users can link in their social credibility so buyers know who they're dealing with even if sellers don't yet have a trade history. Equally important, you can't create multiple Bitcoinary profiles using the same social proof, as once you attach your Facebook, Twitter, or mobile phone number, those connections can't be used again.
Bitcoinary is essentially eliminating the middleman, allowing people to become their own exchange. Quite simply, if you have a computer and access to a local currency, you can become a market maker for that currency. You can do it with gold, cash in an envelope, in person exchanges, rupees, dollars, anything you want. The site itself suggests the possibility of in-person international exchange for travelers, which could become an important niche for Bitcoin.