The potential problem is that you've just described a malware author's dream.

I know it's probably an unpopular opinion, but I don't believe that we should be distributing APKs outside of the Play channels. It takes us back to the PC distribution model, with all of the associated security and usability problems.

Do you mean the old PC distribution model with security and usability problems, but not the must be connected to a network constantly problem?

Not allowing apks via bluetooth seems like a usability issue too.

Yeah exactly, and this seems to be the reason that android doesn't allow apks to be sent over Bluetooth, so we haven't really found a solution so far unless you count swapping SD cards.

Really? Perhaps you know more than I do, but Android "not allowing apks to be sent over Bluetooth" seems pretty unlikely to me.

It doesn't allow you to easily get at apks you've downloaded from the Play store, if that's what you mean, but I think that's just an anti-piracy measure. An apk you've downloaded from somewhere else is, as far as I can tell, just another file. I can't imagine why (or how!) it'd stop you from exchanging them, particularly if you have some sort of custom Bluetooth client.

Does it really try to stop you?

Yeah if I remember correctly the built in Bluetooth file transfer actually won't send an apk, which was definitely surprising to us too. We could send it over our custom app, but that's the problem - what we're trying to send is the custom app itself.

I always send my apk via email, and my friends will install it. what's the problem with that? apk is a file, just like jpeg, mp3. rename it to whatever you like and then transfer.

You'd have to check if the block is solely based on the extension. If so, what about disguising it in a videofile with instructions on how to set it up?

Yes, I always name my .apk files to .jpg before sending over bluetooth.