One of the great advantages of RSS is that it can provide specific information to be integrated and used any way you like. Diluting it with content that makes it less effective for your special use seems inconsistent with this.
I'd suggest a service that creates just the advertising feed you want. Go to Banana Republic, enter your sizes and wait for the right piece of apparel to scroll your way. That would be useful. Sign me up
I still don't entirely understand RSS, how you can incorporate the feeds into your site, how it relates to XML .... ahhh the trials and tribulations of being a non-techie. Anyone care to email me and explain?
[later: I've since done some diggin around on Chris Willis' blog and he has some great basic stuff for anyone who's in the same boat as me. Check out this, this and this .... and this.]