Look for when the environment is changing - the big shift now is mobile Internet. It's really happening big-time. The way you interact with services on a smart phone compared to the Web is quite different, so there's a huge opportunity. ↗
Skype is easy enough to use so that people don't need to be tech savvy - a lot of users just want to communicate with their friends and family, and they find this is the easiest, cheapest way. If you can use a Web browser, you can use Skype. ↗