Didn't you know that's how some people browse porn nowadays? 😀
Actually I must say I never open more than 10 tabs when I browse porn.
90 tabs isn't for porn, it's for news stories. Open 10-15 sites like macrumors, then start command+clicking to every story that interests you, and before you know it you have tons of stories open in tabs.
And bam, Safari is frozen, you can't do anything, other than close all tabs and start over, this time with less tabs.
Firefox usually crashes with that many tabs, but Safari 5 has absolutely no problems with high load. I once opened 200 tabs just to see if it can hold it, it does.
But 5.1 i.e. Webkit2 isn't polished enough yet. The whole premise of Webkit2 is to make Safari perform better under high load, because it sandboxes all content, apart from Safari application itself. In 5.0 if you open 90 tabs, it works, but the application is quite slow in response, in 5.1 the application works nicely but the content doesn't.
This wouldn't be a bug if Safari 5 performed the same way, but this is a step back. The only reason I use Safari as my primary browser is its stability under very high load. I don't want to lose that in Webkit2.