In the eight years that I have been responsible for filing taxes in the United States, I have never once received an accidental tax return from the IRS, nor do I know anybody who has. It appears that with auditing and other efforts that the IRS has been able to overall offer accurate tax returns to the citizens of the United States.
I would not want to get an accidental tax return from the granddaddy of butt whipping. I work hard for everything I get and don't want any discord with the IRS. Some might see this as some kind of windfall but it truly is bad Karma to take what does not belong to you. Live right and make good choices is my motto.
I have never been 'fortunate' enough to gain an accidental tax return from the IRS. I do believe that they exist however, and that they can cause difficulty and problems if they are not detected quickly. As this is the IRS' error though, I do believe that they should pay for any inconvenience caused.
The only way the IRS is going to offer an accidental tax return to taxpayers is if there was a problem on a large scale. With the current governmental deficit and auditing problems, an accidental return is less likely to occur unless something develops during their audit that is going to affect hundreds of thousands of taxpayers.