IRS relies on voluntary compliance, but they audit a few returns with the hope that one person audited will tell ten friends that bad things happen when you cheat on taxes.  Likewise, if one DIYer gets help here, not only will he come back for answers to more questions, perhaps having achieved Level 1 or Level 2 from the time spent already, but he will tell ten friends that it's much friendlier here than at the TurboTax forum.

Practitioners who like to answer questions for DIYers are, as far a I know, not prohibited from visiting the TurboTax site.