If you were to copy the ads and use them to TEACH a principle then they could be used under "fair use". Be sure and attribute.

A few years ago I created a short course on email marketing and used some of the emails I had been sent by marketers. I printed out the emails and then edited them, and used them to illustrate both bad and good points to my clients.

It's always good to have permission to avoid lawsuits.

Aloha,

Jason