Geolocation services are today more commonly referred to as location sharing. Facebook's announcement of the enhanced functionality of Places and Deals on their social networking site will accelerate these services' movement into the mainstream.
Facebook Places opens up the APIs that had been exclusive to foursquare since their inception. This means anyone can write a foursquare-like application with users becoming "mayors" and earning "badges" Foursquare created a custom site for the recent elections: http://elections.foursquare.com/ With Facebook Places, anyone will be able to create such custom location sharing sites and apps. Facebook Deals is fascinating and should provide a huge amount of momentum. Coupons on mobile devices and cell phones have long been talked about. These services will effectively make the conjecture reality and will do so overnight. Out of the gate, dozens of high profile retailers will be offering location sharing based deals and offers.
While not mainstream today, location sharing definitely is the next big thing and will be mainstream within the next year. The internet is fast transitioning from the desktop into the physical world. Location sharing will play a significant role in this shift in user behavior.