Those at least give you neverending variety. There are novel thousands of new variations on the lolcat theme every day, and no end to the slot-machine-like fun of rating people hot or not in the hope of eventually getting to one who is either particularly hot or hilariously not.

But once you've posted in a sample of your own writing, gone "Hahaha, I write like Mario Puzo, hey guys, guess what?", I find it hard to imagine anyone coming back time after time.

That is true. There's a lack of stickiness to the original poster's app as it is. It might be interesting to see how other people's writing was rated.

The newsletter addition was a good idea. I have a feeling many "writers" would be upset to learn they wrote like Dan Brown, no matter how many novels he's sold. Possibly a "From Brown to Updike: How to Improve Your Writing" course.

The OP's idea is darn viral, however. I love the success he's had.