I bought then in 2006 (which was a trial in itself) to put on a stamped, self-addressed envelope to send to a book publisher the USA. As it happened, the company I was sending it to changed their policy and allowed me to send them my manuscript without a SSAE if I gave them permission to throw it away rather than send it back. Needless to say, they did indeed throw it away.
Nowadays, publishers accept submissions by electronic means, so I don't need the stamps. I'm not even sure they still work. Also, thanks to that write-a-novel-in-a-month thing that happens in America every year, there's little chance of getting pulished there anyway these days without the right connections. Sigh.