A friend of mine used to shun my tax guy, saying he was sticking with H&R Block because of how reliable they were.
A couple months ago, he got a letter from the IRS saying 'Thanks for the check, but, uh, did you mean to file any taxes?' Apparently H&R Block had done all the normal work, told my friend how much he owed (when really, he should have gotten a refund, but anyhow) and then neglected to actually file his taxes.
He's asked for the number of my tax guy this year.