I enjoyed this chapter. Anytime the Dursleys get their just deserts in a story is enjoyable. You are weaving a great story keep it up.
As for the taboo being on the morsmordre being stupid I disagree. To the Ministry of Magic and magicals in general the secrecy of their world is important. A floating symbol like that would not be good for keeping that secret. I am sure that is one of the reasons the Death Eaters cast it.
Author's response
Thanks 'fan,
I know I'm gonna catch hell from many reviewers as to why I didn't have the Dursleys roasting on a spit, but I figured this way was more painful for them. (Snicker!)
The taboo: While the floating Dark Mark is bad for the secrecy stature, it's usually the last thing done before the Deez scram. Basically my point is this. They apparently love to start out their playtime with a few rousing bouts of Crucios, so why not set the taboo on that? If the taboo was set to Cruciatus, or the AK, they'd be under fire -before- they got the chance to send up the Dark Mark. Casualties would be reduced and perhaps the ranks would be...thinned.
Alorkin