It's a little more than sneaky. Every study ever done on human/software interaction shows that the vast vast majority of people will never venture outside of the defaults they know very well that most people won't enable blocking. Given that Ghostery is owned by an ad company (Evidon) with a vested interest in trackers not being blocked, I don't think they can be allowed the benefit of the doubt. Privacy software that's specifically built to trick people into thinking they're protected isn't privacy software. Sorry if I come off as a bit of a conspiracy theorist here, but misinformation campaigns by ad companies really bother me.
The relevant sections of the graph are http-set-cookie-responses, cookies added-deleted, and probably local storage sections. Most of the tools they're comparing themselves to don't block first party cookies and stuff, because it's pointless. I haven't looked into the numbers, so I can't tell you exactly how much that skews the results.
Nobody should have their info sold to anyone! If there's anything that people own, it's themselves. (Relevant book: Who Owns the Future, by Jaron Lanier.) Ghostery is the only tool on the linked list that goes behind your back and sells your data to the highest bidder (Maybe DNTM does this too, I wouldn't be surprised). They can't advertise themselves as a privacy solution and then sell out their users to ad companies. Well, they can (legally), but everyone should call them out for doing it.
A bit late to the party, sorry. I'm one of Ghostery developers, feel free to ask questions, tho it may be answered faster if you post on our support board.
So, Ghostery does not bill itself as a blocker, therefore we leave everything unblocked at the start so the user may decide what they're comfortable with. This may change in the future through additions to the Ghostery wizard -- its the first thing that should have popped up for all of you upon installation of Ghostery. The very same wizard also has a section where user is told that they need to select what they wonna block, or simply, block all.
Ghostery is not owned by an ad company, but by a company that offers privacy compliance to advertising and publishing industry. If the difference is not obvious to you, I suggest you read up a bit on what Evidon does on its web site. In short, Evidon provides privacy controls that businesses purchase to allow their users to control their privacy settings on their web-sites, in their apps, or directly in the advertising that may be delivered to the user. Evidon is not vested in keeping the users choices "unblocked", in fact it does not care how users configure their installation.
Cookie assumption that julia makes are not valid. Ghostery monitors all types of cookies and will block them from creation or editing if a web site requests: first party, second, or third. This is reported on the areweprivateyet.com same way as for all other addons listed there.
Ghostery does not do anything behind users back. You are referring to the GhostRank feature of addon that is disabled by default. If you do enable it, Ghostery will then send data about trackers found on web-sites as you browse the web. The data is about trackers, not about the user -- Ghostery strips all identifiers both on the sending end (extensions installation) and on the receiving end (our servers) specifically so the data cannot be used to backtrack to any of the millions of users that have GhostRank enabled. For even more information about this, please read this article:
http://purplebox.ghostery.com/?p=1016023438
Finally, there were some questions about open source and Ghostery. Ghostery is currently not open sourced, tho it was for a long time. It will be open sourced again in the future, but its taking time to do this, hopefully late this year we will have at least one of the releases opened. That said, Ghostery is a browser extension, as such, its written in JavaScript and is not obfuscated in any way unlike some of the others mentioned here. If you are interested to see whats under the hood, feel free to download any of the releases, rename them to .zip and unpackage anywhere to see full contents.
Cheers.