Problem: Asus Nexus 7 not recognized by adb when correctly installed and connected
Setup: Asus Nexus 7 tablet Windows 7 64 bit OS
Steps taken:
An important note about Nexus 7: There is no option for USB debugging readily available in the device Settings for 4.2.
http://forum.xda-developers.com/showthread.php?t=1989777
"Open Settings, then go to phone details (where u can see kernel, Android-version etc) then just tap your Build number 'JOP40C' 7 times!"
This sounds ludicrous, but after I did this, the developer options unlocked and I was able to see my nexus 7 in Eclipse (mac, Mountain Lion) for debugging.