digikam-0.10.0_beta7 (from kde-testing) won't compile given the ebuild's DEPEND. In particular, the following libs are needed from KDE (pre-)4.2: kde-base/libkdcraw kde-base/libkexiv2 kde-base/libkipi Workaround (as of 2008-24-12): Unmask and upgrade to version 4.1.85 (from kde-testing) of the above packages.
We can use kde_minimal="4.2" when it gets to release. Up to then we simply wont bother, if you want it you should know what you are doing.