One of the big issues I have with Pocket isn't even the privacy problem, it's the integration. Firefox would (IMO) be better served by having such things as extensions included in the default distribution. They could even make a separate tab in the extensions dialogue for them, perhaps hidden behind an about:config preference. That way anyone who doesn't want them could disable them and speed the browser up.

There was some discussion of doing things this way back when it was still called Phoenix. The Seamonkey suite was bloated and slow, Phoenix was the stripped-down browser that just did web browsing but had an extension system to add in extra features. But instead of adding features through the extension system the Mozilla team decided to add them into the base.