eBay putting their sellers description in an iframe (a web page embedded within a web page) will hinder organic search engines from indexing that description. As a general rule bots will not crawl frames.
This hidden sellers description is being served up from another eBay top level domain name ebaydesc.com which would not be associated with the sellers content listed on eBay.com further hindering that sellers item from being indexed in organic search.
It's my personal opinion that eBay is doing this to further control what's visible to shoppers using their internal Cassini search engine.
Another thing worth noting. Meta Keywords are OUT and have been out for many years in Google's search crawlers algorithm. Simply put Google and Bing do not follow to Meta Keywords or use them to influence your pages indexing rank. They DO consider your articles wording to decide if your webpage is indexed and under what category. If that text is hidden they can not see it.
So if your wondering why your eBay descriptions are not finding their way into Google search.. Walla! Yesterdays eBay Critic Radio show ECR008 podcast is here: http://tinyurl.com/m2n4dvf