Don't back up anything on iCloud, ever.

iCloudKiller

NSString* doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString* lib = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0];

float version = [[[UIDevice currentDevice] systemVersion] floatValue];

if (version < 5.1)
{
    u_int8_t b = 1;
    setxattr([doc fileSystemRepresentation], "com.apple.MobileBackup", &b, 1, 0, 0);
    setxattr([lib fileSystemRepresentation], "com.apple.MobileBackup", &b, 1, 0, 0);
}
else
{
    NSURL* url = [NSURL fileURLWithPath:doc];
    [url setResourceValue: [NSNumber numberWithBool: YES] forKey: NSURLIsExcludedFromBackupKey error: Nil];
    url = [NSURL fileURLWithPath:lib];
    [url setResourceValue: [NSNumber numberWithBool: YES] forKey: NSURLIsExcludedFromBackupKey error: Nil];
}