There isn’t much you can do to protect your feed content that a scraper can’t use Yahoo Pipes and a few cute regex’s to sidestep. Blocking Yahoo pipes is not the best idea since people actually use it for non-nefarious purposes. Here are a few things you can do (with PHP?) to prevent the regex filters meant to remove your tracking pixels and other stuff from being removed without undesirable consequences.

Dynamically generated tags – Very basic regex filters can be defeated if you place a dynamic class in front of your tracking pixels:

<img class="92934abc123" src="yourimg" />

Chance are the autoblogger won’t bother to sort out all the different image classes. This won’t prevent them from removing all images (or tags) though. How about some slick html then?

Set this up for RSS only:

<img src="" alt="
Your plaintext excerpt here.
">

Maybe you could add a fake ad to that:

<img src="http://ads.yourdomain.com/fakead.jpg" alt="
Your plaintext excerpt here.
">

Or fake feed flare:

<img src="http://feeds.feedburner.com/~ff/slashfilm?a=ynIB-icScgo:Hzwy1PtmAKc:I9og5sOYxJI" alt="
Your plaintext excerpt here.
">

Another (unproven) idea is to use Google’s newfound acceptance of cross domain canonical tags. Basically, you just throw it in there and hope Googlebot is a little relaxed as to where tags show up.

<link rel="canonical" href="http://yourdomain/thepost/" />