If the extra initial scrutiny is perceived to streamline the process and avoid further hassles, many will hand it over without giving it a second thought.

For example, many people have voluntarily submitted fingerprints in order to enroll in TSA's PreCheck.

That's a very good example, but on the other hand fingerprints aren't likely to accidentally "incriminate" you.

Coming into the USA, if I saw that on a form my first instinct would be that not providing it reduces the risk of accidentally getting flagged for something ridiculous. I'd hate to be pulled aside for extra screening because a tweet from 6 years ago included the word 'explosion' in it.

All the people who think that if a form field exists, they have to fill it out. I bet they'll harvest an extraordinary amount of data by having this optional field.

And those who leave it blank will be considered suspicious.

I could imagine that a good LinkedIn or GitHub profile might help support an O-1 or P-1 visa application by providing some evidence that the applicant is well-regarded in their field.