Prius owners in Georgia are discovering that their cars aren't road worthy, at least by letter of the law. Part of the emissions test used collects exhaust samples from an idling vehicle, since the combustion engine in a hybrid shuts off when idling, the Prius registers an aborted test and fails. Owners still have to pay the $25 testing fee. This strikes me as another case of the law (or in this case the test) failing to keep up with new, green tech.
The sting for hybrid car adopters doesn't end there. As mentioned at the recent recording of Bayblab Podcast Episode 8 (in press), governments are offering financial incentives to 'go green' in the form of tax rebates. Prospective buyers shouldn't get too excited about that just yet. The credit is on the taxes paid, so trade-ins and leases can expect to see far less than the advertised rebate amount. It's a similar scenario in the US where a non-refundable tax credit is offered, meaning that if your tax liability is less than the advertised rebate after applying all other credits, that's all you get (discussion forum).
Finally, it should be noted that not all hybrid vehicles are created equal. There are a number of hybrid technologies out there. Some, like Toyota's Hybrid Synergy Drive, are full hybrid drivetrains can run on just the combustion engine, just the batteries or both. Other cars advertised as hybrid may be so-called 'mild hybrids', which can't drive in a full electric mode but rather just shut off the engine when stopping or coasting resulting in a 10-20% improvement in fuel efficiency. These are otherwise essentially conventional vehicles, but still bear the hybrid mark.