For those stuck on the Google Splash Page, can't even get to the Nexus splash screen or are in a reboot cycle, can't get into recovery mode, adb isn't recognized and so on, go to this link:
[Guide] Nexus 7 Bootloaders/Recoveries/Root/Back to Stock - Nexus 7 - RootzWiki
If you don't have your own boot image file, download the stock JRO03D file. The link has you use your command prompt on your pc to manually input commands to Fastboot. I had the same issue as you guys and this fixed it.