whether they are looking the other way on jailbreaks or not, this sounds like a rather serious security problem. it's nice that i can run my own code on the device, but that also means that any mp3 files i download off the internet can run other, potentially malicious code.
Thankfully, this is the Kindle Touch, not the Kindle Fire. I"m guessing maybe 1% of people will use their Kindle Touch as an MP3 player, so this is mostly positive news - A jailbreak vector with little damage seen in the wild - the potential is their, it's just unlikely to be leveraged.