I do a fair amount of procedures (mostly injections), and one thing I must do prior to every injection is obtain informed consent.
Getting informed consent often takes longer than the procedure, in all honesty. (I mean, how long does it take to stick a needle in a shoulder?) First, you have to tell the patient about the procedure, including the risks and benefits (I always accidentally write "injection" as a risk, meaning "infection"), then you show them the consent form. And they have to sign it, which in the case of my patients, can actually be a bit of a process. And then I have to track down someone to witness the consent.
And THEN there are about five or six other places I have to sign and date the form, like to say that I verified I have the right patient, that I'm injecting the correct side, etc.
Recently, I was near a colleague of mine who was finishing filling out the consent form and he started grumbling, "This form is ridiculous. You have to sign it like ten times."
He was right. But here's the thing: for every place you have to "sign and verify", it's because somebody else did something stupid. We have to sign that we checked that we're injecting the correct side, because obviously a bunch of people injected the wrong side.*
So in that sense, I do think it's important.
But in another sense, if you're signing and dating the form five minutes after the procedure, I'm not sure how much it's going to help those errors. And I bet that's what 90% of doctors do.
*A favorite quote of mine:
"If you have the fever, there's only one cure; take two tickets and see the game Sunday morning. Warning: tickets should not be taken internally."
"See? Because of me, now they have a warning."