Scott Burns writes about a study on equity indexed annuities (warning PDF). Here is his summary

“…the study estimates that “between 15 percent and 20 percent of the premium paid by investors in equity-indexed annuities is a transfer of wealth from unsophisticated investors to insurance companies and their
sales forces.”

Benchmarking against a simple $100,000 portfolio consisting of 60 percent 10-year Treasury strips and a low-cost S&P 500 index fund, the two researchers did a Monte Carlo analysis of probable returns. The
simple portfolio beat the equity-indexed annuity a whopping 96.9 percent of the time.

Moreover, after 10 years, the expected benefit of the equity-indexed annuity was only $219 when it performed better, while the expected benefit from the simple portfolio was $33,650 when it did better. Drs.
McCann and Luo concluded that EIAs cost the investor about $153 for every $1 of possible benefits.”