We're still gathering details on the fairy-tale wedding Google's glamour geek Marissa Mayer is having this weekend. The latest: Guests are murmuring about some sort of tracking system that sounds as creepy as SkyNet — or Google itself.

Mayers' three-day nuptials at the San Francisco Four Seasons, where she lives, were announced via an elborate invitation, a heavy red box covered in a velvety material, as we've reported previously. That sounded about right for the fashion-conscious overachiever.

The Google VP's obsessiveness apparently extends to security, as well: The invitations indicate guests are to keep some sort of ID card on them at all times during the weekend, we're now told.

And said guests aren't sure what this means: Are these "smart" cards implanted with radio "RFID" tags? If so, guests could theoretically be tracked across a 135-foot radius with a stationary receiver. Or maybe they'll be simple credit-card-style tokens with a magnetic stripe, swiped on demand. Or maybe former cheerleader Mayer has something more festive and creative in mind. If you've got a clue, do share it with us.

Requiring that guests basically wear a tracking tag will certainly further the image of Google as Big Brother. The search giant tracks a staggering amount of personal data, and company executives have lately been clumsy in answering mounting media questions about the info-hoard. Then again, some of Mayers' guests will be fellow Google executives; perhaps having a taste of their own medicine will have a moderating effect on the data Google collects.

Speaking of which: Though Mayer is employee number 20 at Google and has great power within the company, it's not at all clear that co-founders Larry Page and Sergey Brin will be in attendance at her wedding. Mayer was not invited to Page's private-island wedding to Lucy Southworth, a source close to the event tells us, so she could hardly be expected to invite Page to her bash.

In any case, a tracking scheme will certainly help Mayer keep out the likes of Valleywag as her wedding party makes its way around the Four Seasons, even as it reinforces her rep as something of a data-hungry cyborg. No worries Marissa; we'll try not to take it out on your gift.

(Pic: Mayer, by Esther Dyson)