Tennis balls in the dryer?

I just got back from the laundromat (how two people generate 4 loads of laundry per week I will never understand) and saw a woman put tennis balls in her dryer. I was stumped...and fascinated. The woman only spoke Korean so I couldn't ask her why, but when I got home I looked it up and found a slew of uses for old tennis balls. Below are some laundry uses. Others (give them to dogs, hang in garage to know when you are in far enough) were not as exciting: Got this from The Frugal Life

Put two or three tennis balls into the dryer with your just washed pillows and as they dry, the tennis balls will knock out any lumps that will form in the pillows if you try and dry them without the tennis balls. And if you have too many tennis balls, then share with other people who wash their pillows regularly. - Erin

Keep old tennis balls to throw in the washing machine with shower curtain liners....they add friction so that you can remove the "slime" from the dirty shower curtain. It's important to wash shower liners once a month or so with either a little vinegar and detergent or bleach or ammonia (don't mix the bleach and ammonia it'll make poisonous fumes) to keep nasty fungus' like the ones that cause ringworm or athelete's foot or plantar's wart from growing.

I always put 2 or 3 tennis balls in the dryer when I am drying a blanket or something larger - to help it turn better, instead of continually falling back on itself. It saves drying time.

Who knew?