This was just done to be funny - we really don't Facebook THAT often - I don't condone this as some sort of ritual, it was funny to me and it was original.
I have a lot of family scattered around the country and we all use Facebook a lot to keep in touch. So when Tracy and I were engaged, most of my family found out via Facebook because we updated our statuses.
I surprised not only my guests, but also Tracy by pulling out my phone and posting on Facebook and Twitter from the altar during out wedding.
I had her phone ready in my pocket, so when she asked for it I could hand it to her. No one knew about this except the minister, and myself.
Here is the twitter post:
http://twitter.com/TheSoftwareJedi/status/5925126890