At cms2005 I talked with Tony Byrne from CMSWatch about the architecture of umbraco and how we've focused on keeping umbraco slim and simple, and extending it through plug-ins. I
claimed that umbraco was 10.000 lines of code (aka 10KLOCs), but as it was a while since my last check, I though I'd research it more thorough.
And it turned out to be a very nice surprise; actually umbraco is only 7.548 lines of code! And totally including the web editing client (complete with development environment, etc) and all default plugins and rendering the total is 25.258 lines of code.
That's around 25KLOCs for a complete web development framework including a CMS and a number of plug-ins that let's you
create new functionality with out writing a single line of code, just using your mouse.
But to sum up - umbraco is only 7.5KLOCs and not 10! Less is really more ;-)