Traditional exit strategies for companies include being acquired or an IPO, but that’s normally for companies that have at least an inkling of an idea about how to make money. Unfortunately for many “Web 2.0” companies (like Ajax homepages, Ajax IM clients, online calendars) it’s a tough proposition since what they’re offering is essentially free somewhere else and has been for many years. People who start these types of companies are banking on the idea that users would be willing to pay for the convenience of having a traditional desktop application available online, but it’s a harder sell then they imagined.
Some startups in these spaces get acquired (like Userplane) but only if their offering fits in neatly with the new parent company, and that’s not always the case. In the case of Kiko, they are apparently selling the company/app/domain not because they think it’s a failure, but because they believe their time and resources could be better spent on other ventures. What those other ventures are, who knows, but let’s hope they’re attached to business plans.