Until I see how they are dealing with fraud instead of just shafting their merchants I won't touch anything Dwolla no matter how pretty they think their api is.
I don't see any reason to use Dwolla instead of Paypal if they are going to handle chargebacks the same way.
As much as I hate Paypal, you will earn more money by being able to receive credit cards from different countries through Paypal than being restricted to US customers and forcing them to wait 5 days to get money to Dwolla.
"If a transaction was reversed, what can I do?"
per http://help.dwolla.com/customer/portal/articles/99253-if-a-t...
What you can do:
You may request a copy of the affidavit from Dwolla, who will forward it to you. If you choose, you can then take further action directly with your customer who filed the dispute with the bank.
If you were intially the receiver of the payment, you may send a money request to the other party by logging into your Dwolla account. If you were intially the sender of the payment, you many send another payment to the other party by logging into your Dwolla account.
What you can do:
Contact the other party to work out a resolution.
What you can do:
Contact the Financial Institution directly to see if your account has been closed or is no longer valid.
What you can do:
Contact Dwolla to inquire about verifying information to ensure the account is reopened.
Links? Nothing obvious I am seeing even with a search for "how Dwolla combats fraud"
Additionally is there any difference (for a merchant) in how Dwolla handles chargebacks vs. a credit card company?
But this is my biased opinion as a Bitcoin user (and former Dwolla user). Please go read about it yourself. Perhaps others will come to a different conclusion.
I run Bitfloor and was hit with similar fraud as Tradehill (on a much much smaller scale) and Dwolla was just as ignorant and dismissive of it. Fundamentally, they went into a business that they did not understand. I know this to be true because early on (even before any Tradehill incident) we emailed them to ask about ACH chargebacks and how they handle them. They claimed there were no chargebacks and this was everything I needed to know about their lack of understanding.
A while back I recapped what happend between myself and Dwolla and why they are not a useful service.