I hereby announce the removal of my FunWall and SuperWall. If the interface makes it so hard to send a birthday card that everyone EXCEPT the intended recipient gets the card, the application is functionally useless.
On the one hand, I can't actually be sure who I send anything to. On the other hand, I can't be sure anyone actually intended to send me something. As far as I am concerned, that basically means the product does not perform any function.
Frankly, most of the applications on Facebook don't do much of anything other than ask you to get your friends to join them. I've tried a lot of applications.
Most of the applications send something to your friend. Nice. I can send you text, pictures, sounds, or video. I can't really send you chocolate or a hug. I can send you a picture of chocolate. I can send you a picture of a kiss, or of something more lewd, but I can't send you a real anything. I can send you virtual good Karma. Can Karma actually be good if it is virtual? Can it be good if it is Viral Karma? Let me just give a hint to the people developing one more app to send one more thing... thanks but no thanks.
Causes, eh. I haven't seen anyone leverage them.
Comparing taste/knowledge in certain areas: has potential for strengthening friendships, but not much.
Games, now there is something I can, um, use. And I do mean use. I'm an addict.
The potentially useful applications are for meeting people. Honestly speaking, however, most people are only using these for dating. Nobody is using the "Meet New People" application to find professional colleagues or even like-minded friends to share with.
But the real problem and downfall of all the applications is that the developers render them completely useless by insisting you add 20 of your friends in order to use them. They don't just ask you to do that when you join the application, but at every possible juncture. You can't play a game without being asked to challenge your friends. You can't send Good Karma without being told your Karma is only as good as the number of people you spam with more Good Viral Karma. You can't see someone's profile picture without links to applications YOU added that you could force them to add too (yes, I have set those so I don't see them, but...)
The bottom line is that these applications don't understand about creating real value. Real value is knowing my friends' birthday. Real value is meeting new people. If you create real value, I will really want to invite my friends to use your application, or they'll see it on my profile and want it. If you aren't creating real value, you might want to ask yourself what you are doing.