Why does M. S. Dhoni always take back a stump after winning a match?

When questioned about it in an interview to the BCCI.tv, Dhoni said: “That’s my retirement plan. The good thing is that I do collect a lot of stumps but the bad one is I don’t put a mark as to which match they were from. So, after I retire I’ll watch the videos of all my matches, look closely at the sponsors logos on the stumps and figure out which match a stump belongs to. It will be my post-cricket pass time!”