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So, products/widgets/10 might be OK for a search engine, while
might not be fetched by any crawlers because it has 2 variables. Though I am seeing more dynamic stuff indexed than in years past, it's still a consideration to keep in mind. :)
And of course you can even go one step further and use an URL like:
(assumed that the category #123 contains pages on marketing)
In other words: With mod_rewrite it's easier to use URLs which tell the user what they will find behind it.