CSS Killswitch
csskillswitch.com
csskillswitch.com
I was able to get into some sites I formerly had access to because my private key was never revoked. It was a bit of irony to use that same "unauthorized" access to remove my own key from the authorized_keys file.
Oh, and by the way, don't do that. It's liability-hell, and probably illegal in most places, too.
After you've signed up:
"Here's a handy little text file with your login credentials. Might be smart to save it somewhere..."
http://csskillswitch.com/csskillswitch_pistoriusp.txt
Yeah, I got text Rick Rolled.
An interesting idea, and could definitely work with some clients. If nothing else, it could temporarily damage them, which if they haven't paid up, they deserve. It does seem like something they could pay a web guy a few bucks to diagnose and fix, though.
If they knew it would only be a few bucks from "a web guy" they would likely be able to fix it themselves.
I think it's seldom (never?) I'd actually want to go this route [partial payments along a project helps reduce how much I have at risk], but if I were considering such... rather than a blank page, perhaps a display that said something like "A database error occurred. Please contact developer of this site." That might help the site owner read the subtext ("Payment is way past due.") and not make visitors wonder, "Why isn't my Google working on your site today?"
There are a lot of very small and nice elements in this page worth stealing in a future project- kudos.