So there is a simple hack you can use almost all across the web that I only recently found monetary value for. You can tell me what you think the ethics of it are, but let me first explain to you what I'm talking about. To participate in this, all you need is a Gmail address.
What I found out a long time ago from a friend is that Gmail has 'dot blindness,' or in other words email@example.com is functionally the same as firstname.lastname@example.org, email@example.com, and firstname.lastname@example.org (etc..). If you send an email to any one of those email addresses, they will end up in your inbox (assuming that's your username).
Now the big question is...how can I use this new found knowledge to my advantage? Simple. First case is with Twitter. As someone who builds web apps now and then, I also like to get Twitter handles for those projects on occasion. Twitter doesn't allow you to sign up multiple accounts on the same email address (very similar to almost every single service out there which requires an email on sign-up) because usually that's the unique identifier in their records database. With this cool dot blindness knowledge, you can know sign up an infinite amount of accounts using just one Gmail account with varying numbers of dots. And as I breifly mentioned earlier, this can be applied to almost every single web service that requires an email and you would like to have multiple accounts for whatever reason.
Now the second way that I've found use for this, that also has some monetary value, is the new Red Robin Royalty Card promotion. If you get a loyalty (or royalty) card from them, you get a free appetizer within 15 days of registration, and a free burger on your birthday. All you need is an (unique) email! Well... needless to say. I may have found my way to several free appetizers and free burgers on consecutive months. You figure out how I did it. Should be easy if you've been paying attention.