Version: 2.0.90 (using KDE 4.2.3)
Installed from: Ubuntu Packages
Adding URLs of files that are accessed by smb:// kioslave (e.g. by dragging them from Dolphin's application) is broken - they are not added to the playlist. Thus it is impossible to play files over network from Samba shares. This is a regression since 1.4.10 where this feature works (more or less)
AFAIK dropping URLs from external applications was fixed a while ago (after beta1 though).
I don't think that the issue is specific to the SMB protocol. It will probably yield the same result with any other protocol. Pleaes test again with 2.1 final when it's released.
I upgraded Amarok to version 2.1 (from an Ubuntu experimental repository). And unfortunately still smb:// links are not added to the playlist.
*** This bug has been marked as a duplicate of bug 178691 ***