There is a number of eclasses which export src_prepare(), and additionally hacked src_unpack() for older EAPIs. Sadly, some of them needlessly export that src_unpack() in newer EAPIs as well which just makes ebuild devs confused (especially if that's indirect inherit). Considering that EAPI5 is coming, I think it's a good moment for them to finally stop exporting these functions when they don't benefit anything at all.
