Well, I think what it really comes down to is what your business is. If your business is storage, get good at doing your own storage. If your business is web applications, get good at web applications. Then there are companies on the cusp. Flickr is clearly storage heavy enough that they need to be a storage company. 37signals, on the other hand, stores attachments and some pictures, but it their primary function isn't storage - it's the interaction with that stored content.
Is storage such a thing for your business that you're willing to put a lot of labor behind its solution? Or is storage important to your business, but as long as you get something reliable it doesn't have to be the most efficient possible because it's a small part of your business relative to the other things you do (like HTML, CSS, Ruby/Python/Perl/et al., MySQL/PostgreSQL)? Your time might be better spent on other company work than on storage.
Is storage such a thing for your business that you're willing to put a lot of labor behind its solution? Or is storage important to your business, but as long as you get something reliable it doesn't have to be the most efficient possible because it's a small part of your business relative to the other things you do (like HTML, CSS, Ruby/Python/Perl/et al., MySQL/PostgreSQL)? Your time might be better spent on other company work than on storage.