SPG foursquare Check In Terms

BY LINKING YOUR STARWOOD PREFERRED GUEST® (SPG®) MEMBER ACCOUNT AND YOUR FOURSQUARE® ACCOUNT AND BY PARTICIPATING IN THE SPG SOCIAL CHECK INS PROGRAM (the “PROGRAM”) YOU AGREE TO THE FOLLOWING TERMS & CONDITIONS:

You must be a member of SPG and have an account with Foursquare Labs, Inc. (“Foursquare”) to participate in the Program. Membership in the SPG program is free at www.spg.com. A Foursquare account is free at www.foursquare.com.
Only one SPG member account may be linked to a Foursquare account, and both accounts must belong to the same person.
Only one check in per property per member per 24-hour time period.
All Program offers are subject to the terms and conditions found at www.spg.com/foursquare, which may be modified or discontinued at any time.
Program offers may only be redeemed through a valid check in on Foursquare at an official Starwood property venue.
Program offers will recognize only one Foursquare check in at an official Starwood property venue per SPG member in a 24-hour time period.
If Starpoints are awarded pursuant to a Program offer, the redemption and expiration of Starpoints is governed by the SPG program terms and conditions.
Program offers may not be combined with any other offers, incentives, discounts or promotions.
Starwood reserves the right to modify or discontinue any of its offers available on Foursquare at any time.
You authorize Starwood Hotels & Resorts Worldwide, Inc., its affiliates, properties within the Starwood system and third-party service providers (collectively, “Starwood”) to collect, process, use and display information provided by you during the submission process (including any personally identifiable information) for any lawful, business-related purpose, to store the content and other information at and transmit it to various locations, either directly or through its third-party vendors, throughout the world, whether within your country of residence, the United States, or elsewhere; and to contact you regarding the content and other information you provided.
To update your communication preferences or learn about Starwood’s privacy practices, view the Starwood Privacy Statement at www.spg.com, or call 1-877-782-0071 in the U.S. and Canada, or +353-21-4930474 in all other countries to access our privacy information line.
The Program will not affect your communication preferences with other Starwood programs, for which you will need to inform such programs, Starwood directly if you wish to opt out.
You acknowledge and agree that Starwood may receive the following data from Foursquare: your name, email address, SPG number, Foursquare user ID, Foursquare user type, Foursquare venue history, Foursquare user badges and mayorships and check ins at Starwood venues and other venues. To view or learn about Foursquare’s privacy policy, visit www.foursquare.com.
If you choose to opt out of the Program, you may do so at any time by going to http://foursquare.com/settings. Once you opt out of the Program, Starwood will retain all information it has obtained from you or Foursquare to the extent that Starwood needs such information for business purposes, including verifying Starpoints awarded pursuant to the Program.
You acknowledge that the Program uses the Foursquare application programming interface but is not endorsed or certified by Foursquare.
You agree that Starwood is not responsible for any errors or omissions made by Foursquare.
You agree that Starwood is not responsible for any and all technical errors related to computers, servers, providers or telephone or network lines resulting in an unavailable check in.
YOU AGREE THAT STARWOOD AND FOURSQUARE SHALL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES ARISING OUT OF ANY USE OF THE PROGRAM OR OTHER INFORMATION YOU PROVIDED.
You agree to indemnify and hold Starwood, Foursquare and their respective subsidiaries, affiliates, officers, directors, agents and employees harmless from any claim or demand, including reasonable attorney's fees, made by any third party due to or arising out of your breach of these terms and conditions or your violation of any law or the rights of a third party. Starwood’s failure to act with respect to a breach by you or others does not waive its right to act with respect to subsequent or similar breaches.
You agree that any disputes arising out of or related to these terms and conditions shall be handled individually without any class action, and shall be governed by, construed and enforced in accordance with the laws of the state of New York.
Starwood reserves the right to modify or discontinue the Program at any time without notice as well as your participation in the Program if you violate the terms and conditions of the Program.
Starpoints, SPG, Preferred Guest, and their respective logos are the trademarks of Starwood or its affiliates.
All of the Foursquare TM logos (including all badges) and trademarks displayed as part of the Program are the property of Foursquare.

My experience with three properties and four check-ins was that the bonus was only showing as unlocked once I had already checked into the hotel and the local system seemingly updated a central Starwood system that I was now a current guest. It'd be great to get some confirmation from the Lurkers about this.

Just as the SPG/Foursquare T&Cs state, data communications is basically "one way" in that Foursquare data is shared with SPG, not the other way around. You can check-in to any property (at least when you are in the same general location) and unlock specials; but you will only receive the Starpoint bonus credit when Starwood checks there Foursquare data against the reservations and confirms account status, etc.

You acknowledge and agree that Starwood may receive the following data from Foursquare:

• your name,
• email address,
• SPG number,
• Foursquare user ID,
• Foursquare user type,
• Foursquare venue history,
• Foursquare user badges and mayorships and
• check ins at Starwood venues and other venues.

foursquare's and SPG's systems are not linked

I am sorry you took offense to being corrected

Your reply saying the two accounts "are not linked" is not accurate, in any context, I'm sorry; and since you represent Starwood, you should be very clear in your replies about data and privacy, IMHO.