Yes. Aliases are one of the best features Fastmail has, and they work exactly how you're describing -- you just pick a word and you have that email address. (`[email protected]`, or `[email protected]`, or whatever) If you're done with an email address but you don't want to delete it, you can also disable aliases without giving them up, so email will bounce, but you still technically own it and nobody else will be able to register it.

They're not literally unlimited, but the limit is high enough that in practice, you can have a separate email address for every service that you use.

I do have my own domain, but I don't typically use it for most 3rd-party services. The reason I like aliases more is because if I use the gmail trick or my own domain, there's still a unique piece of information that's tied to my name. In other words, it's still identifying.

Most spammers know to strip the pluses from gmail accounts, so you're not really doing anything at all by adding those. And even if a spammer can't guess your other email addresses, they still know who you are. I'm not particularly secretive about my identity online -- I use my real name as my handle. So it's not even always about blocking spam -- sometimes you want to use an email without giving a company a very obvious link to who you are.