I do that too, so far Adobe, Dropbox and LinkedIn are my only real sources for spam (due each of these being hacked). And oddly the occasional spam to an alias I used for the crypto-discuss mailing list.

One additional twist, I keep my site-spesific aliases on a short sub-domain (for now [email protected]) - if I feel the need in the future I can burn down the whole sub-domain, exchanging s.mytld.com for eg: m.mytld.com.