Photoas is a fast spreading malicious application on Facebook, if you receive any such app request from your friend, you should ignore it or block the application immediately.
On approval of the Photoas application, it will send out an massive app request / messages with links to all your friends within Facebook.
If you accidentally or knowingly approved the Photoas application, proceed immediately to Facebook Application Area at http://www.facebook.com/editapps.php and remove the Photoas app for your safety.
We hope the Facebook Safety Team is working towards it to resolve and keep the users safe from Photas and other malicious application threats.