Living with Plot Contrivances: or how I learned to (mostly) stop worrying and love Spike's story

So sometimes the plot has to bend around other things the writers are after.   In a seven year run on TV like the one BtVS enjoyed that has to happen a few times.  Seth Green decides to leave suddenly, and the story bends around his departure.   Sometimes the bends work.  Other times they are, shall we say, less than obviously natural to the flow of the story.

There are two that come to mind with regard to Spike's story.   ( Musings below the cut )