Allan Ides’ paper (see the previous post) includes a discussion of the pros & cons of single-member plurality elections vs proportional representation. In that discussion, Ides replies to the frequently heard objection that, under PR, a voter has no single elected representative to turn to for constituent services.
On the other hand, it is worth noting that under PR/MMD, should a constituent need to contact a representative, she will have a choice among the representatives of her region and may take some comfort in the fact that a member of her party serves as one of her representatives (if that’s the case).
It’s a good point: a single representative is replaced by a group of representatives, with the advantage that at least one, and likely more, are likely to be politically aligned with the constituent.