Great question, Hitman. The obvious answer is that it would likely depend on the units wagered to determine whether this strategy would pay off over time.
Here's my opinion, and it's just that, an opinion--I don't have any data to back me up. I don't always bet on dogs and take the points, but as a rule of thumb I rarely bet against a dawg in his own backyard, especially if the spread is 4 or more. Actually, the Texans and the Cardinals covered at home for me sevaral times this season, good value. I cleaned house when Arizona beat Minnesota outright on 4th & 19 in a meaningless game (for Arizona, other than pride) that spanked the Vikes right out of the playoffs--had to love it!
Maybe some of the big gun RX posters will have solid #s on this. I would be interested to see them. Again, I don't always take the dog at home, but I rarely bet against him. GL Hitman. - El Iguana