They place a burden on our short-term memory, one of the weakest parts of our brains. It only holds about seven items, and they decay immediately. Elsewhere in the report, you say that, after using their Internet phones for a week, people have almost as much trouble performing certain WAP tasks as they did when they first received the phones. But to a great extent, it's about users still being lost after a week, still going down the wrong path. You'll find that people eventually become used to a technology.
People can learn anything.
They will become better and better and better at it. It's just that the WAP interface is particularly confusing, and you do not learn much in the span of week. You are still quite confused after a week. You still make mistakes. You still go to the wrong areas.