When having semantic desktop disabled it is imposible to full-text search emails. Before KDE 4.7 when email was stored in simples files (or at least no in akonadi) full-text serch could easily be done.
This is not a bug. KMail relies exclusively on Nepomuk for fulltext search.
I sort of know that. But it would be nice with a fall-back solution for system where vituoso-t/nepomuk ressource consumption is too much. I mean, it basically never ends consuming cpu-cycle on disk io - but that is another bug.