Facebook allows linking with my Google account so that I only have to sign into GMail to access my Facebook. Wonderful:

Except that once I try to initiate the linking, Google warns me that Facebook will have access to all of my contacts, which includes everyone I’ve ever e-mailed:

What’s the deal? I can’t find any information about what Facebook does with this info, or if they store it, nor any privacy info about it. Why does Facebook even request this information from Google? I’d use this feature, but this is unacceptable.
Anyone know what’s up?