Will Stephenson, the SUSE developer who has been involved with KDE for years, has been brewing this idea for a while and is beginning to take action on this lightweight KDE implementation. "KDE is not intrinsically bloated. At its core, it jumps through a lot of hoops for memory efficiency and speed, and is modular to a fault. But most packagings of KDE take a kitchen sink approach, and when you install your KDE distribution you get a full suite of desktop, applets and applications. The other major criticism of KDE is that it is too configurable. The KlyDE project applies KDE's modularity and configurability to the challenge of making a lightweight desktop. However, what I don't want to do is a hatchet job where functionality is crudely chopped out of the desktop to fit some conception of light weight."
What the Lightweight KDE Desktop project is seeking is to provide a minimal footprint through packaging changes by factoring out optional components of the KDE desktop, configuration / profile changes, and to ship a simple configuration. This lightweight KDE will also focus upon a fast start-up timeby refactoring startkde or looking at other alternative KDE start-up systems.
There's some KlyDE packages being offered right now on the Open Build Service for SUSE 12.3 and there's other progress advancing elsewhere. More details on this lightweight KDE desktop can be found in this blog post.