Does this make sense if you have a long term investment portfolio and you have 300K in equity from your stocks/etfs. If you wanted to buy 200 shares of SPY but did not have the money, you can sell 2 LEAP puts of the jan 19 2013 for 17 dollars lets say. collect 3400 dollars. Then deposit into your account money every month to cover the rest. so that you would have money to cover assignment of the stock. If you do not end up with stock, at least you got a return on money you did not have initially anyhow. and if you do get stock you end up getting it for 118 a share. so you have a break even of 118.
Sell an earlier month and get more premium per day. For ex, 6 mos. out will get you 1/2 the premium for 18 months out. I'd also sell some OTM calls on part of existing portfolio to yield some extra income - and cap gain if assigned.