Trouble with UICollectionViewCell reuse

ViewController.swift

//
//  ViewController.swift
//  NewHiringSwift
//
//  Created by Tomek on 01.08.2014.
//  Copyright (c) 2014 Tomek Cejner. All rights reserved.
//

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
                            
    @IBOutlet var collectionView: UICollectionView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        self.collectionView.backgroundColor = UIColor(red: 1.0, green: 0.5, blue: 0.0, alpha: 1.0)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // MARK: UICollectionViewDataSource
    
     func numberOfSectionsInCollectionView(collectionView: UICollectionView!) -> Int {
        //#warning Incomplete method implementation -- Return the number of sections
        return 1
    }
    
    
     func collectionView(collectionView: UICollectionView!, numberOfItemsInSection section: Int) -> Int {
        //#warning Incomplete method implementation -- Return the number of items in the section
        return 10
    }
    
     func collectionView(collectionView: UICollectionView!, cellForItemAtIndexPath indexPath: NSIndexPath!) -> UICollectionViewCell! {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as UICollectionViewCell

        cell.backgroundColor = UIColor.greenColor()
        
        if let labelka = cell.viewWithTag(100) as? UILabel {
            labelka.text = String(format: "Row %d", indexPath.row)
        }

        // list subviews
        NSLog("--- ROW %d ---", indexPath.row)
        printSubviews(cell)
        
        return cell
    }
    
    
    func printSubviews(view:UIView) {
        if let list = view.subviews as? [UIView] {
            for uiv in list {
                NSLog("%@ tag:%d", uiv, uiv.tag)
                printSubviews(uiv)
            }
        }
    }
    
}