However, Chrome will automatically update the extension.
Things that could go wrong:
* The author could wake up in a bad mood one day and decide to push a malicious update.
* The author's computer could be compromised, and someone could steal the signing keys and publish a malicious version of the extension.
* The author could get bored of the extension and transfer ownership to someone who offers to maintain it for them, but who turns out to be malicious.
* The author could be in need of some cash and could decide to accept one of the many offers they no doubt get from shady parties to buy their extension.
I'm sure the author of this extension would never do any of these things... but I'm not sure enough to risk it. :/