What would have happened if Jaiku had been given investment and time to flourish is going to be one for an alternative history of modern communications - but what is of interest (at least to me) is what Engestrom will turn to next? Having spent two years in Silicon Valley, his address book must be bulging with useful contacts, and he's commented frequently on the social nature of new online services.
His next project could be very interesting! But in any case, we wish him and his family all the best no matter what they turn to next. It's worth pointing out that Twitter was set up by a team of people whose previous project, Blogger, was bought by Google. When they left, they started Odeo, from which Twitter was born. Can Jyri do something similar?