Planet13 - 7:15 pm on Nov 24, 2010 (gmt 0)
They [Big Merchants] typically do not have left nav links that read Custom Blue Widgets, Big Blue Widgets, Small Blue Widgets. (entire keyword hyper-linked)
You are correct - especially if they have thousands of products in hundreds of categories.
One thing that Matt Cutts has said is to take your ten most profitable products and put links to them "front and center" on your index page.
I would also add links to any big money making subcategories below them - if links to those categories don't already appear on the navigation bar of the home page.