Below is the response from the USPS law/ethics department on the question of doing a gift exchange.
I’m sorry for the delay in responding to your inquiry. Yes, it is okay to organize a Secret Santa exchange on your unofficial website, so long as the website makes it completely clear that NONE of the information and activities (including the Secret Santa Exchange) featured on the website involve or are sanctioned by the U.S. Postal Service. You must run the website and all activities related to in your personal, not postal, capacity, and all participants in such activities must also be acting in their personal (not postal) roles.
I hope this is helpful, and encourage you to contact me if you have any additional questions or concerns. Thank you for checking this out with the Ethics Office!
Some basic rules
Please make sure you actually intend on participating if you sign up. The idea of having someone without a gift because someone did not fulfill their end would be very disappointing.
If you sign up but cannot participate for whatever reason, please remove yourself BEFORE the draw date listed on the exchange page.
Above all, let's have fun. We will all need a bit of joy during the Christmas season, so let's make it fantastic for everyone involved.
Joining the Gift Exchange
You need to have an email invitation from the organizer or a link to a gift exchange in order to join an exchange.
Once you have your invite, click on the link that you received from the organizer (either by email or a link from Facebook or Twitter). Simply follow the instructions on the page to RSVP. If you have not established an Elfster account, you will need to create one to RSVP. Multiple accounts may use the same email address, however, each person needs to have their own unique user name and password for their account.
Socializing And Wish Lists Before Names Are Drawn.
Once you have accepted the invitation to participate in an exchange, you will be able to view information about the exchange from your Elfster home page.
You can click on the exchange name, and should see a list of fellow participants, view the information about the spending limit, and how your group is going to exchange your gifts. You can add items to your own wish list, and your wishes will remain on your list until you remove them.
A sign-up deadline is set up for your exchange. Once this date has passed, you will receive an email from Elfster that includes a link allowing you to see the name you have drawn in the exchange.
Adding To Your Wish List
To add items to your wishlist, click on SHOP at the top of any Elfster page. If you are already in your wish list, you may also click on the yellow Add To Wish List bar.
You may SEARCH Elfster for gift ideas by typing text into the "What are you wishing for?" box OR
Add a link from any website for a specific item or URL by clicking on the LINK icon above the search bar, then pasting the full address (including the www at the front) into the LINK box, and choosing Add. Once we've verified the item, you can edit the name or change the image of the item before clicking CONFIRM. If you have more than one Wish List, you may choose which Wish List to add it to. OR
Add a text wish by clicking on the TEXT icon above the search bar. You can enter any ideas or hints you may want to share. OR
Add the Elf It! browser button to your bookmarks bar, which will allow you to add items to your Elfster wish list from any website with the click of a button. Click on "Get the add to wishlist browser button" above the search bar on the SHOP page to add the Elf It! browser button to your bookmarks bar.
Finding A Gift For My Draw
To get ideas, you can view the profile for your draw by clicking on the name of your exchange, and then clicking on the gray box where you see your draw's name or the View Wish List. You will see their full profile page.
If they do not have any items on their wish list, or you want to learn more about them, you can click on the "Ask a Question" button to send them an anonymous question or two. You may select from our suggested questions or create one of your own! This is a great way to have fun with your exchange.
Marking Gifts As Sent & Received
When your exchange is underway, you will have the option to mark your gift as sent or received once you have placed your gift in the mail, or gotten your gift. This can be found by clicking on the exchange name from your home page. The next page will allow you to Mark as Sent or Received. If you are marking a gift as sent, you will be asked to enter tracking or shipping information that will be sent to the recipient to let them know a gift is on the way, but they will not see your name. If you are marking a gift as received, you may also send a thank you note to be sent as an email as well as a post on the exchange Gallery wall. This note may also include an uploaded photo of your gift.