I think you've made a good choice, oh_no, but that is different than a wise one.
What I mean is that, at least for the next few years (as long as the Fed keeps interest rates low), I think you'll see a good return on Annaly. just seemed more likely, but should the dividend decline to "only" 10-14% (versus the 17% it once was), that's still a fantastic return on a stock that is selling for less than book value.
That said - it is usually very risky to buy a stock without caring what the underlying company does, or what its financial status is. High yields, a track record of rising share prices, and a variety of other metrics can all exist for a time related to a business with a terrible business model that isn't sustainable. If you only invest by the numbers, and especially if you feel your eyes growing wide at the prospect of huge and/or quick returns, you are usually likely to be stung and disappointed in the end.
In this case, though, you probably lucked out. What you should know is that Annaly's business is borrowing money at the current very-low interest rates, and reinesting that money into Federally-guaranteed, mortgage-backed securities. Since those securities are backed by the government, there is zero risk of default. Annaly makes its money because it receives more interest on the money it is lending than on the money it is borrowing, and it boosts that profit by using leverage (essentially, lending more than it borrows (which, to any newbies reading this, may sound impossible, but it is actually how much of our financial system actually works - or doesn,t, depending on your perspective).
You should be aware that in years to come, when you start seeing headlines that the Federal Reserve Bank is planning to increase interest rates, the time to sell this stock will be near. Annaly's expenses will go up as a result, and since it's leveraged its profits will probably go down a lot. But Mr. Bernanke has promised to keep interest rates low at least through 2014 . . . and I expect he, or his successor, will be forced to keep them low a lot longer than that.
Till that happens, Annaly is a good stock to buy, IMHO.