A year ago while still in a closed beta, Google Voice had 1.4 million users, with 570,000 using the service 7 days a week.#1
Skype added 39 million users in Q4 2009, to come to a total of 560 million accounts.#2
Its still early for facetime, but I wouldn't discount Apple, especially with over 120 million iOS devices sold.#3
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#1 http://www.zdnet.com/blog/btl/business-week-14-million-googl...