In addition to the overhead, this has rather significant privacy implications, since you're sending your complete browsing history to a third party (and in real-time).

And the third party is SearchYC, run by "a couple of guys". They don't even have a privacy policy.

That being said, I don't fault the SearchYC guys for this at all- the extension leverages their site far beyond its original intended purpose.

Something like StumbleUpon has similar privacy implications and yet, people don't seem to have any problem with that.

When I was thinking about my implementation, I didn't think about SearchYC but instead was thinking about scraping the homepage (and its 7 little brothers) for the relevant info and then compare it to the current page. It would remove your concern (besides the initial setup) but would work only for recent stories. (which might be good for some people but not all)

I'll do a bit of cleanup to the extension. Then I'll post the code, so you can change what you like.

The greasemonkey script and chrome extension parse HN's newest items page in addition to searchYC. You could just disable the call to searchYC in the script.

You may be correct. All I did was convert the original script from using GreaseMonkey's proprietary functions to Chrome extensions. I found it very useful that I don't have to check if a site was on HN. I get a many pleasant surprises this way, on sites I never thought were here.

Perhaps just have it send out for comments when a page has been opened from HN. That way I can click a page from HN and see the comments on the underlying page. So have a conditional lookup based on referrer.