Contact synchronization is the backbone of social networking, in my opinion. Your "friends" are in your address book. Syncing them on all your devices is a key element of your social life. I always said that the company that manages to "own" your address book will own the war of social networks.
Among those that tried, definitely there is Plaxo. Thursday, they were acquired by Comcast. Just when they started moving towards mobile (they are using the Funambol client for Windows Mobile).
Friday, ZYB was acquired by Vodafone. They are a pure mobile address book sync, based on SyncML. Cool company. I met the CEO and I am happy to hear he is a rich man now. He deserves it because I have seen plenty of mobile sync companies but ZYB appeared to me as the best one from the get-going. And Vodafone is the biggest name in mobile. An acquisition by them means a lot.
Now, if service providers are out acquiring mobile contact sync companies, what does it mean?
That mobile contact sync is hot ;-)
If you are one of the service providers that is thinking "and now, what can I do?", I have a suggestion for you. Check my.funambol.com. It works as well as ZYB and Plaxo, when it comes to contact sync (and probably a bit better ;-) You can have it branded and with push email as well. Just give me a call. I have set up a hot line for contact sync yesterday...