That's a really interesting idea. I know HN has a bookmarklet that lets you not have to come to the site if you want to post content as you're browsing the web.

I also don't suspect the querying would be a problem. Most web app problems are IO bound and so long as you're using web servers that support async IO, it's unlikely to be a huge issue except at massive scale - but even then you just throw more servers at the problem as it scales in a linear fashion.

And should scale still be an issue, hopefully the site will be decentralized by then and some of us will prefer to query our home node.