Earlier quoted context omitted.
A shopvac (or any vacuum not designed for mercury) would be a really bad idea: they vaporize the mercury and seriously distribute it around the house.
I agree with you both, but that doesn't change that I suspect this would be the default approach for a lot of people that have neither the money nor the ideology to justify a professional cleanup. An easy example of this kind of thinking is that people used to (and many still do) bury used motor oil in their yard. (See e.g. http://www.experienceproject.com/question-answer/How-Can-I-D... )
http://www.bloomberg.com/bw/stories/1991-04-28/old-motor-oil...