It does raise a red flag that they would be asking for it in the first place. But it could be a legitimate site. If they are a business and paying you, like Blasting News, it's possible for them to want your ID.
A scanned copy can be uploaded to a password enabled, legitimate account. Name the copy something else, like BCWYAF.jpg or some name that absolutely no one would be searching for.
Do NOT name the copy "mypassport" or with your name or address or anything identifiable.
Make sure the site is absolutely legitimate too. Do a BBB search, or a google search like "nameofcompany complaints"
The site you are uploading to should have a "lock" symbol and they should plainly state their reasons for requiring personal ID and the reasons should be legitimate.
But again, I would be extremely hesitant to upload personal ID to the internet.