What are examples of planned obsolescence?

I ran across this example recently. I had a 20 year old vacuum which died. Went to the store for a new one since there were no parts available to fix the old one. Asked how long I could expect the new one to last and was told "about 3-5 years". When I asked how this could be because I just had one from the same manufacturer that lasted for 20 years, the gentleman said "planned obsolescence" which means that the manufacturer planned on the vacuum to die after a few years so that I would have to buy another. Good for their checkbook, bad for mine. Placing sweeping tail fins on an automobile was an example of planned obsolescence.