French business media are reporting that Viadeo, the professional social network challenging LinkedIn in a number of countries, has acquired Soocial, a Dutch contact management, syncing and backup service provider (via Journal Du Net).

The service basically lets users sync all their contacts across their smartphones, email accounts and computers, and lets them manage, clean up and share contacts from their digital address books.

Soocial has been around for quite a while – Erick reviewed them back in April 2008 – and is probably best known for blatantly hasseling the Hoff.

Financial terms of the deal were not disclosed, but Les Echos says the transaction was worth ‘multiple hundreds of thousands of euros’.

Viadeo claims its business social network has over 40 million registered users and is likely looking to expand the number of services it can offer its members in the future.

Update: the news is now official:

As part of the acquisition, Soocial’s development staff will be joining Viadeo to work towards improving overall user experience on the Viadeo professional social network.

Also read: As Viadeo Shelves IPO, LinkedIn Set To Begin Trading On Thursday (May 2011)