Back in 2010, Mitt Romney deducted the cost of maintaining (feeding, brushing, training) his wife's show horse, Rafalca, as a business expense.

A lot of people ridiculed the idea that Rafalca was a business, arguing that, because Rafalca didn't generate any revenue, the horse was merely a hobby. But, assuming Rafalca was actually a business, that's kosher. Maybe the Romneys regarded Rafalca as a startup enterprise that would eventually produce revenue, or an asset that might eventually be sold at a gain.

In any event, the Romney's apparently no longer regard Rafalca as a business.

How do we know this?

Because the Romneys didn't deduct the cost of Rafalca's care and feeding from their 2011 tax return.

So, what changed?

Why was Rafalca a business in 2010 and a personal hobby in 2011?