"We try to engage with everyone, even if it's just to welcome them to the Seamless world after their first order or to agree on a particularly yummy food choice," says the Twitter team at (), an online food-ordering website that pairs customers up with local restaurants that provide door-to-door delivery.

Companies that provide services also like to congratulate and celebrate with their customers.

"Each day we respond to a handful of complimentary Tweets and say 'thanks' and celebrate alongside our customers, who are excited about being done with their taxes," says TurboTax's Morrison.

It shouldn't come as a surprise, but if you mention a company's name on Twitter, the company probably knows about it. That's because companies monitor Twitter for mentions of their brand name, mentions of their competitors, and general trends that affect them.