I buy them to bring to work because my co-workers stick their mugs and empties right up on to the tap, touching it and spreading their germs. I want just water and not some leftover coworker spit and lipstick with my water.

Watch out for those re-used plastic bottles as with time they're a real bacteria factory! Better to get those indestructible "Nalgene" type bottles that don't take odour/colour (even if you fill them with spaghetti sauce or beets) and are easily washable.
One way to avoid bacterias is to fill said bottle with vodka which is also real good for being punk in drublic at summer festivals, but I digress.

There are other even more serious problems with most plastic water bottles (I wrote about it before here)

http://geekent.com/blog/archives/001681.html

Also, not to mention, there's no regulations on bottled water as there are with tap water, and in many cases our tap water is much purer that bottled stuff.