Foursquare's Dennis Crowley responded to that Facebook is taking on location tagging with Facebook Places; "We're still a platform for location, specifically around sharing locations though check-ins, surfacing interesting things around you and using game mechanics to encourage and reward for certain actions and/or behaviours."
Foursquare also "most sign ups" ever on August 19th.
"Facebook also launched a location platform, which appears to be mostly based on checkins (and common FB elements like comments / likes / photos)," he added. "We already allow users to publish their 4SQ checkins into Facebook News Feed and we'll eventually going to allow users to push them into Facebook Checkin Feed. "I'd imagine we'll probably pull FB checkins into 4SQ too. We're in middle of a redesign and some new feature launches, so we're going to get through those before getting started on FB integration."
Crowley also said that Facebook photos are bigger than Flickr, but it doesn't make the latter any less of a successful service.
Note: Emphasis are our own.