Twitter looks to be going the way of a number of other LBS-related applications with a feature (the firm is prototyping) that allows any given end-user to find tweets within close proximity to their location. Given their recent PR-snafu (and subsequent fallout whereas they reversed a privacy update) LBS-related applications are still not without their issues too.
(Source) Design & Trend: http://goo.gl/RTz3H1