When Sun reported on their first implementation of shared libraries, the paper they presented (I think it was at Usenix) concluded that shared libraries made things bigger and slower, that they were a net loss, and in fact that they didn't save much disk space either. The test case was Xlib, the benefit negative. But the customer expects us to do them so we'll ship it.
So yes, every major operating system implements them but that does not mean they are a good idea. Plan 9 was designed to ignore at least some of the received wisdom. -rob
