Driverdan, maybe you're right... but what about the "featured tweets" from Twitter? They are bulk, unsolicited and adv messages... You're a spammer if you don't pay? Otherwise if you're Twitter you can do everything? Just to understand...
You seem surprised that a company treats itself differently than random users of its service. I'm surprised that you're surprised.
It's kind of like saying "I don't like paying for coffee, so it's OK for me to break into Starbucks at night and steal some." It's not, because the terms of the transaction aren't that. They're "if you give me money, I will give you coffee" and you can agree and trade money for coffee or disagree in entirety and go without the coffee. You aren't allowed to walk in, take the coffee, and quip "I'm altering the deal; pray I don't alter it any further."
It's pretty cut and dry.