Here is a good place to get a basic education on annuities.
http://www.bogleheads.org/forum/viewtopic.php?t=990
Personally I prefer to mange my own risk vs paying someone else to accept it. It also has a company risk of who is providing the product. Advisors push annuities because they make a profit by selling them. Maybe a SPFA (single premium fixed annuity) might have a place in some portfolios, however a good AA (asset allocation) balanced regularly, invested in low cost index funds with broad diversity is a much better option for most. Very easy to manage yourself in an hour a month and a better success analysis (Monte Carlo analysis) over the average retirement span. And you retain more of your own money in the end.