The picture describes it all: One's man trash is another man's treasure. In this case, it's one team's trash is another team's treasure.
There are different reasons why a player might be placed on waivers. The most common one would be a players lack of production. Another reason is to free up some cap space. Then there is the rare occasion where you can only shake your head and wonder as to why they placed a certain player on waivers.
Here are the top 10 NHL waiver pickups after the 2004-05 lockout.