I like that it is optional, by default. If they could make Pocket more optional, by default, I would be very pleased. YES, I am aware you can disable it via "about:config", but most users do not play with such things. I'd like to see the option to disable Pocket via the actual control panel (basic user settings). With that said, I personally would likely enable new feature as I would like to know if the site I am using has been compromised in the past. Although, I'll wait until this is released in its final form as I'm avoiding legacy stuff and will use this once it is updated.
I never tried pocket but isn't it by default deactivated (you only see the icon) which you simply can drag & drop outside your visible area (hide it), from what I know it's not 'activated' it's just only the icon and you need to click on it. Normally there should be no connection to the pocket service unless you activate it. But I'm not 100% sure I mostly use user.js before I start Firefox the first time.
It technically still loads, from what I gather. It is not activated in that you've not signed in to use it, but it still does load with Firefox. I'd like a standard option to disable the load. For now, I guess doing it manually via "about:config" is good enough, though it is not obvious for the basic home user, who would be clueless.