One reason to grab your own domain, use Google's Apps For Your Domain, and set up a catch-all address.
The pizza guys know me as papajohns@<domain>.com, Best Buy knows me as bestbuy@<domain>.com, my bank knows me as bank@<domain>.com, etc. And they all get caught by my catch-all, spam@<domain>.com.
Once I trust a place, and know they aren't all spammy, I can move them from being caught by the catch-all to being an alias of my personal account.
The thing that surprised me was how few places sell my address. I'm only being spammed on 3ish addresses I've given out, and none of those are ones given to 'big' companies.
FastMail.fm also has a similar service. You can use <something>@<username>.<domain>.<tld> and messages are automatically put into folder <something> in your account.
Cool I didn't know that. That'd make finding the spammed address even easier...
But... FastMail costs money for anything more than a 10 meg inbox. I prefer the 6+ GB (and growing) of inbox space for free that Google gives. And all the power of the google search engine to find my emails for me.
Well, it's easily defeated. But it's a nice feature of email addresses that more people might like to know about. And at least you won't get false positives if someone defeats your trap with the sed approach.
Sadly it never works as my spam seems to have all additions filtered out. All the .'s and I assume that by removing the + I don't get the spam anyway. :/
