Who receives the error email notifications of a failed Flow process?

The flow creator is the one who always receives emails for unhandled faults. You'll want to open the flow and resave it using your credentials so the emails will come to you instead.

Edit 08-03-2020

While the above was correct at the time it was written in 2015, see @AnveshThakkallapally answer below which discusses the Summer 18 updates that allow an admin to change this behavior without needing to re-save a flow.

Good News with Summer'18 release: When a process or flow interview fails, Salesforce sends an email with details about everything that was executed and what failed. Now we can decide on who should be receiving the flow error emails irrespective of who deployed/last modified the flow/processbuilder

Step1: Go to setup>email administration>Apex exception email> add as many user you want (you can also add external email addresses) who needs to get the flow error emails from salesforce.

Step2: Go to setup> process automation settings> change the drop down value of "Send Process or Flow Error Email to" from "User who last modified the process or flow" to Apex exception email recipients