This might be old news, but when I went to the knot via my phone the very top of the page was a link to an article about 10 things that are just "tradition" and you don't need to do anymore... UGH. It's on the mobile website front page.
2 - You must invite everyone with a guest
"It's still polite to invite guests' significant others, but if you're inviting a group of coworkers, for instance, and two or more of them are single, they should have no problem attending solo."
(ETA: I read this as if she's saying SOs can be optional in some circumstances. If she's actually just making an argument for not inviting singles with a guest, then fine)
3 - Your registry should consist entirely of housewares for your new home
"You can register for anything from honeymoon hotel accomodations to skiing equipment"
"but nothing should stop you from creating a honeymoon or otherwise 'untraditional' registry"
"feel free to include a ping-pong table for your basement or a complete DVD collection on your wish list if you can't use yet another kitchen appliance."
6 - You have to have a rehearsal dinner
"You can skip a rehearsal dinner"
"Having a RD is still smart when your and your fiance's parents aren't acquainted, but if there's no time or room in the budget, then it's ok to skip it, especially if your ceremony rehearsal has to take place on a weekday."
"Ask anyone who tells you otherwise if they'd like to plan and pay for it!"
Really? REALLY?
(They also have a whole rule about how its ok for your mom to throw your shower. I'm less judgy on that but still on the fence.)