I completely agree with user20368. Not having the ability to undo a reconciliation in the standard QBO package is ridiculous. I'm a small business owner, handling most of my own bookkeeping. Quickbooks online is FAR from perfect and not infrequently makes an error in downloading a bank transaction (it sometimes enters a deposit as an expense in the register, for example, or downloads the same transaction twice, or loses a transaction). And of course, I'm human, so sometimes I make a mistake or do something wrong. 

Having to manually un-reconcile every transaction, one at a time, is beyond frustrating or annoying. It is one more thing that makes me hate having to use Quickbooks. I cannot perceive any valid reason to reserve that feature to only the "Accountant" version, other than to drive people to pay more for your software. To be blunt, it sucks.