I don't ever recall a time when a web page that I was loading pegged my CPU. I agree that tabbed browsing is embarrassingly parallel. But, are web pages particularly CPU bound? If anything, it's the bandwidth that's throttling the development issue.
The hard core javascript guys I know talk about developing interesting client side code compare it to developing the old 8 bit computer games, and trying to do something really cool and interesting with 64K of memory. They're trying to do something interesting and bundle it up in 64K of code, so the download speeds don't cause people to bounce to another site.
I don't ever recall a time when a web page that I was loading pegged my CPU.
I see this occasionally due to browser bugs. (This is tautological, since I define pegging the CPU as a bug.) In some sense Chrome is the first postmodern browser: instead of trying to eliminate bugs it lets you kill -9 tabs.
The hard core javascript guys I know talk about developing interesting client side code compare it to developing the old 8 bit computer games, and trying to do something really cool and interesting with 64K of memory. They're trying to do something interesting and bundle it up in 64K of code, so the download speeds don't cause people to bounce to another site.