You can have a fair-to-middling programmer in the bay area locally, or the best programmer in all of Michigan remotely. What you lose by not having people locally you gain by having better people, in theory.
This applies to any locale as well. If you limit your search to only those people within driving distance of your office, you're almost guaranteed to get a lower caliber dev than if you were able to hire any dev in the world.
Put that all into an imaginary 1-100 rating: you can get a 60-70 programmer in the bay area, or an 80-90 programmer remote. How many points does being local make up for? That's a question specific to your company, but if it's less than that difference in overall developer quality, remote may be a good call.
First, web apps aren't that difficult, it is true. But that doesn't stop web app startup founders from demanding only the best of the best data structure/algorithmic programmers.
Second, web apps are not even close to being the only kind of programming, suitable for remote work or not.