Except for the CPU you can do that on a Mac Mini too. But I don't really consider a so-called barebones laptop to be a true home built computer. The ones I've seen come with a motherboard, LCD, battery/power supply, etc. With a home built desktop you can choose all of those items for a true custom built system, whereas your choices are very limited with a barebones laptop.

The bad thing about barebones PCs is that if you screw it up who are you going to call? You are the CS rep, so get ready to call yourself and complain about the thing working wonky! Yep, no warranty either, except for individual parts. That might not matter to some, but it is certainly a consideration for many.