(petitioner, former NFL player, was advised by Denver lawyer to invest in horse breeding program which turned out to be a tax shelter; petitioners invested over $13 million into the program which generated large losses for seven years; petitioners attempted to deduct losses, but IRS denied them on grounds that activity was a hobby and losses subject to hobby loss rules; $4.4 million deficiency upheld; no accuracy-related penalty imposed because petitioner not sophisticated in tax and relied on attorney in good faith).