Hi Nicolas,
All I can say is it was a problem for me.
I had to spend hours creating canonical URL's to reflect the structure of my site, and the site is now more difficult to maintain.
I use keywords in my category names because the product names alone do not fully describe the product, so if someone is searching for Strathmore Illustration Paper they'll see this result ...
As you can see keywords in the product category and subcategory are highlighted, Google is using them so having them there is good for SEO.
Please reconsider this design decision, or at least make including the subcategories in the URL an option.
NOTE: the search results shown are Google page one positions 2, 3, and 4 - position one is the manufacturer's site, so I don't think I've been penalised by having a long URL.
Thanks,
Ian