Nexus 7: does ruining the bootloader hard-brick the device? Or is there still a chance to recover?
If you can get the device to boot to fastboot then you can "fix" a brick. 

I have "soft bricked" my devices many times. 

Samsung has "Download Mode", basically their version of fastboot. If you have an image that you can flash, you can recover. The same goes for the Nexus 7. If you have an image, which google provides because they are "developer" devices (as well as consumer). 

The term "brick" is used very loosely and doesn't mean what it meant back in the WinMo days. When you bricked your WinMo phone it was as useful as a paperweight. 

The only true bricks I have ever seen is when something fails in the hardware. Anything else that I have seen there is still a way to get to recovery, fastboot, download mode, etc. If you can get in to any of those you are golden.