Take it for what you will...here is Money Magazine's list of 4 home renovation don'ts, which they claim may actually decrease the value of your home.
A swimming pool. Unless you live in a hot climate, a swimming pool can be a liability, not an asset. If you live in an area that doesn't get much pool-time, the cost of insurance and pool maintenance is a buyer turn-off.
Home addition. Many home additions look unnatural with the rest of the house. Make sure your add-on is well-designed or don't do it.
Trendy finishes. When it's out of style, it will look bad.
A Jacuzzi. Not everyone loves a giant tub with multiple jets.