The main thing for me isn't even blocking ads as such. The main thing is blocking the absurd amount of crappy javascript that clogs up my browser, in which I have no interest.
I find the unfiltered web insufferable these days.
If you want a suggestion for an alternative, I really don't have one. I'm currently using µBlock, which isn't bad, but requires a bit more setup than Ghostery. https://en.wikipedia.org/wiki/UBlock
...If you voluntarily opt into that program (Ghostrank), after reading the straight-forward description.
I don't understand why people find their business model so abhorrent when its entirely opt-in and they don't weasel around what ghostrank does. Surely you must find every service on the internet that you use for free, particularly Google, to be horrible as well?
This is what the ghostery options screen says about the data they (optionally) track:
> This data is about tracking elements and the webpages on which they are found, not you or your browsing habits.