iOS Facebook cannot post on another user's wall

I am trying to make a post on another user's wall using another user using FBConnect. I am using the embedded method of the iOS Facebook API (that is, I am forcing the browser to appear inside my app, so I am not leaving the application at all). This method works for posting into the wall of the same user, but doesn't work on the wall of another user.

Code:

    self.facebook = [[[Facebook alloc] initWithAppId:self.appID andDelegate:self] autorelease];
if ([self.facebook isSessionValid]) {
    [self proceedToPost];
}else{
    [self.facebook authorize:nil];
}

- (void)proceedToPost
{

NSMutableDictionary* params = [NSMutableDictionary dictionaryWithObjectsAndKeys: @"myname", @"name",
                               self.appID, @"app_id",
                               self.title, @"caption",
                               self.link, @"link",
                               @"animateURL", @"picture",
                               nil];
[params setObject:"my-user-profile-id" forKey:@"to"];
[self.facebook dialog:@"feed" andParams:params andDelegate:self];
}

The problem is that authorization is done as expected, but when trying to actually post, I see an error message in the embedded browser "cannot post to user's wall".

Can anyone help me with this?