tedster - 10:48 pm on Feb 18, 2011 (gmt 0)
People do link naturally to product sites - just not to sites that are nothing but lists of products to buy.
It can take some cleverness to create link-worthy content, especially if your products are so generic that people can buy them all over the place. But that gets outside the scope of this forum. It's a business issue, and marketing issue in general.
We do have a Link Development forum [webmasterworld.com] here - and there are experts in the field of building links the natural way - here and around the web.
I do hope your rankings bounce back - if this is an algorithmic penalty, they probably will in a month or so. But for the long-term health of your business, stepping up your marketing game a bit sounds like the best thing you can do.