While writing about the legal implications of Facebook opening an office in Dublin from a Data Privacy point of view Simon makes this point:
It should be clear that a PR person dealing with their address book falls outside this exemption, but that it allows for private people to keep a gmail address book, and even perhaps to check it against membership of Facebook, provided that action is entirely personal or domestic. If a person is in a business where networking or keeping connections was required for their work, it is likely that this would fall outside the remit of the above exemption. [more]
As one of his commenters notes it would be difficult to judge what is domestic and what is not. No mention of leaving the info with the user rather than the service provider as a solution.