I recently shot a small documentary, I have releases for all principles involved. We shot much of the footage at a public event and order to provide context and background I shot a bunch of streeters, man on the street interviews. Do I need a release form for each one of these little interviews

I am in Canada

Where ever possible you should get release forms signed, it's standard practice on everything apart from news. I know production people who get worried if they haven't signed everyone off, it gives confirmation to any broadcaster etc who buys it that everything has been cleared.

You do get individuals who refuse. one well known paramilitary here always refused to sign, but it was thought unlikely he would sue, because he was maintaining his image.

Not sure about Canada's laws, but in the U.S. we get release forms signed by anybody prominently featured on camera. That includes on the fly/man on the street interviews and even broll if we are obviously focusing on select individuals.

I recently shot a small documentary, I have releases for all principles involved. We shot much of the footage at a public event and order to provide context and background I shot a bunch of streeters, man on the street interviews. Do I need a release form for each one of these little interviews

I am in Canada

Picture this... The pres of the Ceeb sees your small doc at a festival and loves it, wants to run it nation wide. They write you a cheque for $2,000,000 and give you season Leafs seats. Allll they need is for their legal department to clear it. They ask to see all your paperwork to cover their butts. No release forms for all those interviews that really tied the whole doc together? Uh oh! Sorry, deal flatlines. Maybe re-shoot the interviews again with new people, show it to them again, ah too late they've got something else in mind now.
Poof.

Always get releases whether you think you need them or not. It's the right way to do it.

What about "camera lice", i.e. those folks who you don't want in the shot but position themselves behind the subject just to be in the video, even though they have no idea where it's destined, or that they may well be forcing a re-shoot?