This seems convenient, but now I worry scammers will use this as another way of getting people to run arbitrary JavaScript on the client's device.
'Instructions' on how to do {x}, but it's also siphoning cookies off to an undisclosed backend.
This is the worry a lot of people have. The only real saving grace is that copying in JS to the address bar doesn't execute the code, and it's a bit of a pain to get bookmarklets bookmarked.