The word 'ToDo' has been trademarked by iphone app developer

Trademarks and patents are totally different protections.

A trademark simply prevents competitors from using your name in their product. For example, I can't call my tissues "Kleenex" because that name has been trademarked. I can still make tissues, however. If Kleenex had an active patent on tissues, I wouldn't be able to make and market tissues without infringing on their patent.

That's a substantial difference. At worst (for competitors), this trademark will prevent apps being named something like "ToDo List" or "Mobile ToDo". It won't actually prevent todo apps from being sold.

Is it the work "TODO" which has been trademarked, or just the graphic associated with it? If it's the word, I'm disgusted - words and phrases in common usage shouldn't be eligile for trademark.

Patent != Trademark