Ask HN: Who should I interview for my Master's Thesis on freemium?

I have earlier used HN and Quora to get some ideas for my Master's Thesis on freemium (http://news.ycombinator.com/item?id=1652597). Now I have chosen what to focus on: optimizing customer acquisition when using freemium. Last semester I wrote a paper on freemium (http://www.scribd.com/doc/46680854/Succeeding-With-Freemium) where I found that word-of-mouth was a core element of freemium, and this will be the focus of my thesis. To be more specific, my focus will be on companies such as Dropbox that incentivizes people to share Dropbox with others to get more space for free, and how that effects Dropbox's freemium model.

But who other than Dropbox should I contact to try to get an interview?

(Also asked on Quora: http://www.quora.com/Freemium/Who-should-I-interview-for-my-Masters-Thesis-on-freemium)