Popularity shouldn’t be the acid test to determine if you should install an extension. The important question is whether it enhances your browsing experience without any nasty side effects. The good news is that the extension community is actually pretty adept at self-policing. Most extensions that are truly “broken” (for instance, they crash your browser or suck up all your CPU power) either get fixed quickly or simply vanish.

Gosh I’m bad I use one on the list all the time,Baldy

Source: Top 10 Firefox extensions to avoid