Alexei, an employee of Ghostery, replied to Google Analytics - 1 / Ghostery - 0?, a question about Ghostery.
Safari's blocking mechanism has several problems that result in blocking not being applied properly, which can lead to cookies. These problems have been reported to Apple.
In this particular case, dropbox.com has a custom script that dynamically creates Google Analytics tracking images in a way that Safari's "beforeload"-based interception cannot catch.
I recommend telling Safari to reject all third-party cookies, which should help with the cookie aspect of the issue.
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Ghostery for Safari is a Safari extension, which means Ghostery depends on facilities that Safari provides to extensions.
Safari's way of intercepting and blocking requests for extensions (the "beforeload" listener coupled with a "canLoad" tester function) has several known deficiencies, this being one of them.
Until Apple provides better blocking facilities, Ghostery for Safari will remain limited in several ways.
