Waste is not the word I would use.
Water only releases humidity into the air... it doesn't absorb it.
The beads are engineered to maintain humiity... meaning they absorb and release moisture as needed to maintain the perfect environment.
Your glass of water could overhumidify and your option is to remove the glass of water, then put it back in and take it out etc... etc...
Beads are worry free, you spritz them with water every so often and they do the work for you.
Here's some more information:
[ame="http://www.botl.org/community/forums/showthread.php?t=1663"]http://www.botl.org/community/forums/showthread.php?t=1663[/ame]