There appears to be no way of setting frictionless requests as on for facebook ios sdk. For Javascript inplementations this can be done in the fb.init method.
The on
In newer version (2/25/2012 and newer) of the facebook-ios-sdk, there is a new FBFrictionlessRequestSettings which you can enable once, and then all future apprequests will automatically be frictionless. So when your app starts, you should do:
[facebook enableFrictionlessRequests];
I prefer this over manually setting the @"frictionless" key to 1 because when you send an apprequest, you will still briefly see the FBDialog pop up and then disappear. If you do 'enableFrictionlessRequests', Facebook.m will automatically set the 'isViewInvisible' param for you and prevent the FBDialog from flashing.