The ability to view tweets from any user based on geographical location could challenge Foursquare and even Facebook.
According to The Wall Street Journal, Twitter is testing a feature that would potentially show tweets sent by any user on the network -- whether that person is followed or not -- in a user's Twitter feed if the tweeter is within the local vicinity.
Existing Twitter users will know that it is already possible to share your location when posting updates, but it's an opt-in, rather than opt-out, feature.
There's no doubt that contextual features are going to be the future of modern consumer technology -- whether that contextual awareness is a smartphone understanding colloquial English, or recognizing that its user is at a boarding gate at an airport and pushing flight tickets and a weather forecast for the destination to the device's lockscreen.
It's equally clear how such a feature would resonate with businesses, particularly smaller companies with tiny marketing budgets.
Foursquare has built its entire business around people "checking in" at specific locations and Facebook recently teamed up with Cisco to offer local companies special Wi-Fi routers that would give Facebook users free Internet access when posting to their feeds that they are on the premises.
However, judging by the furor which greeted Twitter's decision to change its blocking policy last week, it will be interesting to see how its existing users feel about the feature.