claus - 6:37 pm on Feb 28, 2010 (gmt 0)
RESERVE these class names for that special use and not use them for adding CSS styles in any other element:
Those are very poorly chosen class names. Words that are so generic as "photo", "url", "description" should not be used for application-specific stuff. That only opens up possibilities for a whole lot of mis-classifications.
If Google wants to do this properly, they should at least introduce a generic class prefix for those class names, e.g. "Product Microformat Class Name", pr "pMCN_" so that:
"brand" becomes "pMCN_brand"
"category" becomes "pMCN_category"
"description" becomes "pMCN_description"
... and so on. Anything else is asking for trouble down the road.