determine if MKMapView was dragged/moved

This is the only way that worked for me that detects pan as well as zoom changes initiated by user:

- (BOOL)mapViewRegionDidChangeFromUserInteraction
{
    UIView *view = self.mapView.subviews.firstObject;
    //  Look through gesture recognizers to determine whether this region change is from user interaction
    for(UIGestureRecognizer *recognizer in view.gestureRecognizers) {
        if(recognizer.state == UIGestureRecognizerStateBegan || recognizer.state == UIGestureRecognizerStateEnded) {
            return YES;
        }
    }

    return NO;
}

static BOOL mapChangedFromUserInteraction = NO;

- (void)mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated
{
    mapChangedFromUserInteraction = [self mapViewRegionDidChangeFromUserInteraction];

    if (mapChangedFromUserInteraction) {
        // user changed map region
    }
}

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated
{
    if (mapChangedFromUserInteraction) {
        // user changed map region
    }
}

The code in the accepted answer fires when the region is changed for any reason. To properly detect a map drag you have to add a UIPanGestureRecognizer. Btw, this is the drag gesture recognizer (panning = dragging).

Step 1: Add the gesture recognizer in viewDidLoad:

-(void) viewDidLoad {
    [super viewDidLoad];
    UIPanGestureRecognizer* panRec = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(didDragMap:)];
    [panRec setDelegate:self];
    [self.mapView addGestureRecognizer:panRec];
}

Step 2: Add the protocol UIGestureRecognizerDelegate to the view controller so it works as delegate.

@interface MapVC : UIViewController <UIGestureRecognizerDelegate, ...>

Step 3: And add the following code for the UIPanGestureRecognizer to work with the already existing gesture recognizers in MKMapView:

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    return YES;
}

Step 4: In case you want to call your method once instead 50 times per drag, detect that "drag ended" state in your selector:

- (void)didDragMap:(UIGestureRecognizer*)gestureRecognizer {
    if (gestureRecognizer.state == UIGestureRecognizerStateEnded){
        NSLog(@"drag ended");
    }
}