More to the point, showing your skills after you've been granted an interview, and being forced to do spec work before you are allowed to apply (wtf?????) are not the same.

It could be an exercise to build a very simple webapp in 15 minutes. I mean, there are so many 'build a blog in 15 minutes' tutorials out there. It would test if you have enough rails/django/x-framework experience to build a simple crud app.

Besides, this is just a platform, it's up to the interviewer to set an appropriate task. The interviewer can provide an existing web app and ask the user to do something with it, instead of writing something completely from scratch.

The examples given take way less than 10-15mins, though. OF course, they're not really "webapps", just very basic HTTP APIs.

You are right. I meant more of the kind "Hey, before your interview, do this". I misspoke when I said "interview problems".