I expect there are also patterns in other countries?
Also, with VOIP it could reference where a number doesn't have long distance fees, but has nothing to do with where it is.
No, I believe this concept of mobile phone numbers being tied to localities is specific just to a few countries - USA, Canada and I think South Africa - due to how local calls were billed there; and for all other countries the mobile numbers were allocated from a single country-wide pool so their mobile phone numbers have no geographic structure other than the country code.
My thought is something like a phone number, email address, or domain name bypasses this problem. It is fairly trivial to verify you have access to a phone number, email address, domain name. Feels like this is one of those chicken and egg problems though. Why would anyone list their location at my service if nobody queries it and why would anyone query my service if nobody lists their information with me?
Other countries work in much the same way, except the prefixes are, of course, different.
There's also the issue of moving. I have a Florida phone number. I haven't lived in Florida in a long time.
If a phone number is for a mobile phone then looking up the location doesn't make sense at all: mobile phones are mobile.
I guess you could try and crawl an index of business phone numbers and associate those with the listed address for businesses, but that's a completely different business from running a geocoder.
You could provide a bit of geographical information about the first three digits of a US phone number. I imagine that's not what users are actually looking for though.