rocknbil - 8:12 pm on Mar 6, 2010 (gmt 0)
I think FarmVille is a decent example. Etsy. Kijiji. PlentyOfFish. Scrabulous. Google. Ravelry. Twitter.
There's only one problem with this.
These killer apps are the realization of what was once an idea. No idea, no killer app. :-)
And one of the first things I learned about FaceBook was how to make FARMVILLE invisible. :-) More annoying than pop ups, able to drain hours of poeople who are supposed to be working in a single bound . . .