It ain't so difficult to analyze the code of Chrome Extension [1]. I did (I quite often do this before installing extensions that do not have published source) and as much as you should trust random guy on HN there isn't anything malicious in the code.
On the other hand it is not very effective as the block list is quite limited. 33 entires if I have counted well.
Isn’t it a problem that Chrome extensions have been purchased by others who then update the code to add spyware to them? I’ve never been notified about updates to Chrome extensions; they’re quietly updated in the background.
Google controls the extension, they can swap a new version under your radar at any moment. Happened to me a couple of times (ImprovedTube for example "upgraded" to remove features I used). Not any more, I keep all the extensions I use as a local unpacked copies.
On the other hand it is not very effective as the block list is quite limited. 33 entires if I have counted well.
[1] - Check for yourself - https://gist.github.com/chew-z/7b70da3724626ab04cfc9676bee18...