“What happens after Yahoo! acquires you” over at 37signals.com is an interesting read.
Funny story from the Yahoo! trenches: a few years after Y! had acquired del.icio.us there still was no internal bookmarking service. There were a lot of pleas from the tech-minded folks to set up an internal del.icio.us instance, which fell on deaf ears. I believe it was Leonard Lin of the Upcoming team who then installed a copy of Scuttle, an open-source del.icio.us clone, more or less in his spare time, so we had at least some degree of social bookmarking. (It’s rather handy in team environments in case you’re wondering.)