Anecdotally, non-users struggle to understand why they might adopt Twitter and the iPad, but medium-term users seem to derive immense value from them. I suspect this is because they are platforms - providing a framework for other parties to deliver value upon - rather than being applications. Perhaps applications, with narrow use-cases, find quick adoption because of their obvious value propositions, while platforms need a while for the network effects to become obvious.
iPad’s attraction is deeply bound up in apps, and the idea of an instant-on, always-connected general-purpose computer. But the initial use, and apparently for some the only use, is as a browser with a new UI. It’s only really through acquiring a selection of applications that deliver the user value that the utility of the platform becomes obvious.
Likewise for Twitter. When you first log in, it invites you to contribute, but gives you no obvious benefit upfront. While twitter has done a great job of helping people start following others immediately, the real value I get from Twitter is the ability to get a needle-thin narrowcast of news that is super-relevant to my interests and entertainment that I love. Getting to that place has been an exercise in curation, of carefully discovering people that tell me things I’m interested in, and weeding out the red herrings. The value of Twitter has grown in proportion to the effort I’ve spent tuning in to those sources. But that process is emergent and ad hoc; nobody tells you how to undertake that process, but most people seem to discover it on their own.