The API call that Michael refers to is related to the "Stats Monitor" feature of Shareaholic for Firefox that can be turned off at any time.
The Stats Monitor shows users the Compete.com stats for the page they are on. The API call is intrinsic to the functioning of this feature. For example, only by knowing which web page the user is viewing can the browser tool show the user information about that web page or Web site.
To disable the Stats Monitor, go to "Shareaholic Options" -> Display Options -> Uncheck Stats Monitor.
And, all users are now made aware of this feature upfront:
The Stats Monitor is only available in Shareaholic for Firefox.
If not, what is spyware?
Anyways, that is why it was made easy to shut off completely in case people didn't want to deal with it. Also making this behavior very clear in the next update within the extension itself (not just the welcome/upgrade pages). Privacy is critical.
Most people upgrade their plugin via Firefox's addon manager, and skip the "what's new" page that opens up. This is because we trust whoever made the plugin to not introduce any malicious behavior in future updates.
Judging by the intrusive nature of this feature, I believe it should be opt-in rather than opt-out.
Also, posting it to HN without the question mark in your title was totally bogus.