I've just connected 2 boards together the *WRONG WAY*: 7 pins instead of 8.
The result ? Cracking noise, IC parts "exploded" all over the room. OOPS!
The first board is still working, luckily..
Removed the exploded ICs and took a picture:

Time to hunt for more ICs for replacement, hope I can get it fixed..

I had that happen once when I hooked up a voltage regulator chip wrong.
I never would have thought I needed to wear safety glasses when tinkering with electronics!

PS- could you reduce the size of the picture? It messes up the formatting of the forum.

Fixed image size !
Replaced ICs and... it's working again !

Ah yes, you have discovered first-hand the "serious and permanent damage" referred to in the instructions. I'd strongly advise *not* doing that.

(Also: We've recently found a good way to protect the circuit against being plugged in wrong, and it will be added to the next version of the circuit board, available starting in about a month.)

Yes, I did read "serious and permanent damage" referred to in the instructions and thought I lost the board at first. Of course I didn't do it on purpose and will pay more attention next time !
Make sure all pins are connected.. Lesson learned !

Good to know a new version of board coming out! excited