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Where it makes the most sense is when you have multiple product lines to sell. I just don't think it works well (for visitors) for a single product or line of products that would logically fit in one silo.
OK @gooner, so you want an example. I will give you the perfect example: TopTenReviews
These guys are so silo'd up they could shoot ballistic missles out of those things. Check it out. And they sure know how to use subdomains in their silo strategy. I would say they are the best example that I have seen.
Just look at their various categories and spot check their rankings. You'll see. It's not all about silo - they do have a lot of authority. But when you look at how they do it, it has 'silo' all over it.