Note also, that this only reads the last folder, so you can fake a .html file after it, filled with keywords.
i.e.
http://www.domain.com/product/1/fake_file_name_here.html
http://www.domain.com/product/1/other_fake_name.html
Will both load the same product.
You can then build a .html name from the product title.
I use:
{$products[product].product|escape}