When Foursquare issued their update today to v3.0 they removed the BBM integration from the app along with removing it from the Alpha build. Some people have upgraded but didn’t realize they were losing the BBM integration but thankfully there is a way to get back to square one. RR_yy posted some OTA links for both OS 5.0 and OS 6.0 giving you back the previous alpha with BBM support. Others that had issues with downloading the previous alpha may also have better luck with this update.
You can pick up the Foursquare alpha with BBM integration OTA at this link. Let us know how it works for you!