Publishing trends has a good post describing a new variation on spam: creating low-quality ebooks from plagiarized or public-domain content and selling them in ebook markets like Amazon’s Kindle store. If you want to MAKE.MONEY.FAST there are people willing to help:
Automatically detecting these spam ebooks might be a good machine learning project. One problem is that to use features of the ebook itself (e.g., poor formatting) might require purchasing it. But there are sure to be many useful features that the ebook store provides that might support an effective classifier.
(h/t Bruce Schneier)