I have covered this topic before, however I wanted to share my most recent nice email stories! First, I emailed Glade to tell them how much I love their product, they sent me a nice email back, and a coupon for a free candle (the 4.9 oz fragrance collection)!!! Then, thanks to Sandy telling me about her experience, I emailed Bar-S (the people who make those great hot dogs that are always so on sale), and then sent me a $5 off any $5 Bar-S product (so if I catch the good sales I could score possibly 5 free packs of hot dogs) and lots of 25 cent off coupons!! These will triple at Kroger or Albertsons, so if I just watch for one of their good sales, I could potentially get free or near free products! Now, not all companies send you some sort of reward or coupon for saying something nice, but most do! Plus, you're doing something nice for them in return by giving them some positive feedback!
On the other side of that, if you have a bad experience please tell them that as well. I emailed Starbucks about a recent experience and they are sending me 2 free drink coupons! You may think that's not nice to send them a negative email, but they need this feedback to improve their customer service. Otherwise the next person they make angry may not email them, they may just go tell everyone they know and that company may lose lots of customers.
So basically, remember to give feedback!! It's important for all involved and could save you money!! :)