I have encountered a very unusual  and bizarre situation in Twitter. A user with account @hh88hhhh seems to tweet from multiple locations  even though it's nearly impossible he/she can be in these far apart locations! Can location be directly manipulated?
GEO Place Manipulation
twitter;geocoding
When you add a location to a tweet, you have to option of picking the location from a searchable list of various nearby locations. The search here isn't limited in any way, so you can practically choose any location you wish.