I know how to switch between Google accounts when installing apps, I can go to accounts and select a default or when I install the app I can select an account before clicking install. . I have google play 3.5.16 on two devices an HTC thunderbolt ADR6400L and an Acer Iconia A100. I have two gmail accounts one is dmsxx@gmail.com and the other is actually a Google apps account at dmsxx@xxx.us The problem is on occasion I loose the ability to switch which account the app is being installed under. The only way to do fix the issue is to go to settings and apps, clear the cache, force stop and uninstall updates. Once I update Google Market to Googe PLay Store then all is fine for a few days. After a few days I loose the ability to switch accounts and everything defaults to dmsxx@gmail.com. I have emailed google support on this issue before without much success.