Twitter Undershare: Is there something you need to tell the entire Internet about? Actually, there probably isn't. But something about the message-broadcasting service seems to beg people to share too much, 140 characters at a time. You can delete posts, but they still end up sent to people's cell phones and indexed in search engines. Where's the "untweet" button?
Tumblr Unreblog: What happens when your girlfriend follows the same cutie you do on David Karp's kiddy blogging service, and notices your habit of reblogging the Tumblrette's every last quip, pic, and quote? Ah, for a way to instantly zap all of your reblogs! It's either that, or propose a threesome.
LinkedIn Snub: So you meet a "social media marketer" — i.e., someone trying to get paid to talk to their friends on Twitter all day — at a party. You grudgingly exchange business cards. The next day, you get the inevitable connection request on LinkedIn — even though you barely know the twit, let alone feel comfortable recommending their work. The feature LinkedIn needs: A way to politely acknowledge your interaction without actually exposing your whole list of industry connections to them.
Untexting: If AT&T, Verizon, Sprint, and T-Mobile can shuttle text messages from phone to phone through the magical ether, surely they can reach into your friends' devices and delete that hastily sent SMS before it's read and the damage is done.
Get to work, geeks! There's too much information on the Internet as it is. Time to make the world safe for undersharing!