No, it's a feature, showing that those lines are new in the locally-modified version. You can do % svn blame file@BASE for the old behaviour.
Andrey Paramonov wrote on Thu, Oct 13, 2011 at 13:14:35 +0400: > Hello! > > To reproduce: > 0) Checkout a working copy. > 1) svn blame somefile. You will get lines of somefile annotated with > revision and committer. > 2) Modify somefile. > 3) svn blame somefile. You will get lines of somefile annotated with > double hyphens -- revision and committer information not available. > > This is a regression compared to 1.6.12. > > Best wishes, > Andrey Paramonov > >