It would be interesting to know which other privacy plugins that sell data. Current recommendations seem to be pretty unanimously favoring plugins which do not, but it is always a moving target.
In addition to my answer regarding the business model of Ghostery above: https://news.ycombinator.com/item?id=21897809. I'd like to add a few things to address your points:
(1) Ghostery did not "fall completely out of favor", as far as I can see. It is true that in _some communities_ (in particular some sub-reddits), some people tend to recommend different addons instead (often not based on any technical arguments, though), but this is not a trend that can be generalized (more people continue to recommend Ghostery as a very solid privacy protection suit).
(2) EFF's Privacy Badger is not a replacement for Ghostery, for more information about why, we wrote about it in the past[1][2].
(3) Ghostery has an "actual ad-blocker" built-in, in fact, it is one of the most efficient out there as was shown in a study that we published this year[3]. The adblocker as well as benchmarks are open-source and anyone can run them locally to verify the claims. We also more recently wrote extensively about the internals of this adblocker[4].
References:
[1]: https://whotracks.me/blog/how_cliqz_antitracking_protects_us...
[2]: https://0x65.dev/blog/2019-12-19/blocking-tracking-without-b...
[3]: https://whotracks.me/blog/adblockers_performance_study.html
[4]: https://0x65.dev/blog/2019-12-20/not-all-adblockers-are-born...
Ghostery used to belong to a company named Evidon, which had this business model of collecting data to sell it in some form (the feature was called "Ghostrank"). In 2017, Ghostery was acquired by Cliqz (which builds an independent and private search engine from Germany), and since then a few things happened: (1) the extension was open-sourced, (2) Ghostrank was completely removed and (3) Ghostery is now developing paid products as a business model. For example we launched Ghostery Insights[1] and Ghostery Midnight[2] recently, both of which are subscription-based.
[1]: https://www.ghostery.com/insights/ [2]: https://www.ghostery.com/midnight/
As someone who works in this space I assure you the barriers to entry are not that high. If I were to sort the various lists of accounts alphabetically you'd see names like Citadel and Two Sigma flanked by hoards of tiny funds you've never heard of. Many of these funds you've never heard of are 5-10man businesses or teams within larger funds. Making money is much more of an algorithms problem than a resources problem.
However, specifically in the realm of sourcing and processing novel raw unstructured datasets and creating signals that other firms don't have, as far as I know the big firms (some others in addition to the 2 I mentioned) dominate this area, as its too expensive and time consuming for smaller groups to do.
A lot of fundamental hedge funds turned to this in the early 2010s as awareness of big data became a thing, thinking they could close the performance gap with the quant funds. It didn’t work. The quant funds that purchase this data use it as only one dimension of analysis to confirm a hypothesis which has already been empirically tested across many other inputs.
I have a specific example I can talk about, because my old firm abandoned the data: I found a reliable method for predicting exactly how many Model X and Model S vehicles Tesla sold well before earnings each quarter of 2017, including complete configuration data for each vehicle. Even with that KPI in hand, I couldn’t successfully forecast where the stock would go after each earnings call.
Were they leaking VINs somehow?