1. It's the early days. If you've only been on a few dates, I'm not even sure a breakup is necessary, unless someone is truly confused as to why you've disappeared off the face of the planet. But a text message is okay in this instance. You barely know the person. Three or four dates equal about eight hours together. No need for a long handwritten letter. In fact, you probably don't even know your dumpee's address.
2. The relationship was toxic. I don't care how long you've been dating, if the relationship was much more bad than good, you can get away with doing it via text message since an in-person meeting or phone call will probably just devolve into a screaming match or some other major drama. (Crying is not drama. If you're worried someone will cry and you don't want to see it, that is just being a coward.)
3. He's avoiding you. If he's avoiding you and not returning calls, then you have a right to resort to a text message. He probably prefers it that way.
4. It's safer. If your man is abusive or you feel threatened around him, then a text message is the way to go. In fact, I'd definitely recommend NOT meeting up with him. You may even want to forego telling him altogether and just change your number and stay at a friend's house for awhile.
5. He was caught cheating. Dude doesn't deserve more than a text message.