Why don't you use RDFa, after all, the example you gave " overstock.com ", they are using RDFa Here is the excerpt from that page...
<ul itemprop="breadcrumb" class="horizontal-list bcrumbs">
<li typeof="v:Breadcrumb" class="bcrumb-1">
<a property="v:title" rel="v:url" title="Online Shopping" href="http://www.overstock.com/">Online Shopping</a>
</li>
<li typeof="v:Breadcrumb" class="bcrumb-2">
<span class="bcrumb-arrow"></span>
<a property="v:title" rel="v:url" title="Office Supplies" href="http://www.overstock.com/Office-Supplies/22/store.html">
Office Supplies</a>
</li>
<li typeof="v:Breadcrumb" class="bcrumb-3">
<span class="bcrumb-arrow"></span>
<a property="v:title" rel="v:url" title="Office Furniture" href="http://www.overstock.com/Office-Supplies/Office-Furniture/310/dept.html">
Office Furniture</a>
</li>
<li typeof="v:Breadcrumb" class="bcrumb-4">
<span class="bcrumb-arrow"></span>
<a property="v:title" rel="v:url" title="Office Chairs & Accessories" href="http://www.overstock.com/Office-Supplies/Office-Chairs-Accessories/3637/cat.html">
Office Chairs & Accessories</a>
</li>
<li typeof="v:Breadcrumb" class="bcrumb-5">
<span class="bcrumb-arrow"></span>
<a property="v:title" rel="v:url" title="Ergonomic Chairs" href="http://www.overstock.com/Office-Supplies/Ergonomic-Chairs/22529/subcat.html">
Ergonomic Chairs</a>
<i class="last-child"></i>
</li>
`
And I can explain everything here but I strongly believe that I can't match up the explanation given by Google.
So, in case you have not gone through these explanations(links below) I strongly recommend you to go through them. I hope these will solve your problem.