Facebook invented, and Google have just generalized, an entirely new class of application. Take Dopplr. It's a social network that does trip tracking and coincidences. This is completely backwards - the social network stuff is overhead that we have to implement so that we can keep trips private and restrict the list of coincidences that you have to manage. Dopplr should really only be about the trips.
Facebook and Google have suddenly enabled a class of application that is the interesting half of this - I can think about the functionality, and sit in someone else's social network while I do it.
Paul Mison makes an interesting distinction between profile-centric and media-centric social networking services - Facebook being profile-centric and Dopplr, or Flickr, say, being media-centric. This evolution benefits both media-centric services (because they can avoid having to implement all that profile-editing overhead) and profile-centric ones, because they get events to drive return visits. Even heavyweight media items that take a bit of effort (a Flickr photo upload, a long-form blog post) tend to have lighter things attached (comments, usually), and these do very well at driving return traffic.
My house contains many clocks. Most of them are attached to computers and tend to sort themselves out when the clocks go back. A couple are manual and need poking at by hand, which isn't really a chore till you have a house full of them. But the wall clock in the kitchen is Magic - it just needs a battery, then it'll go pick up the time from Rugby and set itself. It'll automatically adjust itself when the clocks go forwards and back. It has no controls at all, as they're not needed.
This means that when it fails, it fails particularly badly. It's currently alternating between just spinning round and round quickly, and telling a time about two hours in the future. And of course, I can do nothing about this. I may replace it with something stupider.
Grrr. If you require, in your application_helper, a gem that isn’t installed, then that helper doesn’t get compiled or included. And no error message is printed. It just silently isn’t made available to your templates.
I wish people would understand that these hacks, and the many, many Facebook application hacks, are not faults of the platform. They’re faults in the application. Every time you lower the bar to producing web applications, you get a barrage of apps written by people who haven’t thought about security.
The Microsoft XBox live newsletter isn’t readable in the Microsoft email client.
I have Leopard now, which includes, amongst other things, Python 2.5.1 and PyObjC built-in. Because of this, I've been able to package Flame as a much smaller application - 70k compressed rather than 3 megabytes. But it'll only work on Leopard. So far, I haven't been able to use Leopard to build a version of Flame that'll run on Tiger (10.4), but I'm sure I'll figure it out eventually.
Lots of folks ask "why doesn't sun just do the JDK for Mac?". The real answer is "because Apple wanted to do it"