Ask HN: At what point is it best to create a business entity?

I've noticed some say it's the last thing they do as r&d is worked on, while others seem to have a catch-all company entity LLC to do contract work under. I guess I'm looking at examples of the ways people decide to approach the business side of things at an early level.

I like the concept of having a legal entity to work under- something that I can have on a card to give out. But that's mostly for side work I would do. Is there anything bad about doing that that I might not have thought about?