I wanted to know if you could integrate a counter of how many users are using the same value in a field ... for example, the location (I live in Italy - 5 user) with popup list users!

That would be a custom modification...

One problem I see with that, though, is that the field is text entry... Is 'usa' the same as 'United States'? There is no restriction on what a user can type in that field. So you'll likely end up with multiple entries that are the 'same' but typed or spelled differently that cause the mod to be almost useless.

maybe with predefined fields would be possible!