As the developer of Disconnect, if you're removing chunks of functionality the site developers expect to be there, you should be doing it in a way that doesn't break that functionality so absolutely.
You could cloak the cookies so they're pageview specific. Or inject your own functions in place of the ones that are being blocked.
Whether analytics is an essential service or not is a pretty up in the air question.
No. I'm suggesting that if you're writing an extension that changes the way javascript works across the web, you should do it in the least intrusive and breaking way possible.
An extension like this changes a javascript load error from a once-in-a-while event to a happens-all-the-time event.
I can't imagine a situation where you need to know analytics are being consumed in order to give users the data they want (unless the site in question is itself an analytics site).
To allow / cause your site to break when analytics aren't served is, in essence, attempting to enforce an unspoken contract between gathering user info and serving them data.
As far as I'm concerned, a site that doesn't work when analytics aren't served is a site I will literally never use.
You could cloak the cookies so they're pageview specific. Or inject your own functions in place of the ones that are being blocked.
Whether analytics is an essential service or not is a pretty up in the air question.