At my university (2001-2007) we had an annual event called The Naked Mile. It’s pretty much exactly what it sounds like. Campus police let it go.
Not sure if they would now.
ETA: I found this little write up about it. As history. Sigh.
Seen a spontaneous unexpected one? No
Seen a planned one? Yes - In the mid-80s, the frats at UCLA had an unofficial annual streak down Hilgard Avenue (sorority row) where the sisters would watch from lawns or balconies. I saw it from the sidewalk.
Been one? Once in high school. Ran one entire block of a residential street in the middle of the day on a dare.
There wasn’t anything particularly sexual about streaking.
We had 3 masked guys streak lunch one day in high school. On the up side, they were all swimmers and thus used to being naked in public (Speedos cover nothing!) On the down side, everybody on the swim team recognized them because we had all seen them nearly naked every single day.
When I was a kid, I called into the local AM radio station (this was when they still played new music on AM) and won a KCBQ Streak Team T-shirt.
Agree. If you let your kids go to an art museum, they’ll see more nudity.
At university (early 90’s) in the UK, I lived in an all-male Hall of Residence, and the ‘Old Boys’ reunion weekend had a tradition of a ‘torch race’ round the quad.
Competitors were nude, and had to clutch a rolled up newspaper between their buttocks as they ran. This was lit at the start of the race.
Running faster meant the ‘torch’ burned faster, so runners were incentivised to either waddle round (prolonging the hoots of derision from spectators) or go as fast as possible before the flames got too close to sensitive parts. Hairy-assed runners were particularly nervous.
I never competed, but did do a ‘naked yard’ of beer as a requirement for election to the Hall’s student executive committee.
1975 Canadian football league championship Grey cup game had a streaker. It was a (ahem) “thing” back in the day.
We call this ‘grooming’.
Don’t tell republicans, they’ll burn the art museums down. 
remind me to not try to post things well past my bedtime in Japan.
I saw one at University of Maryland Baltimore County back in 96 or so. He was running between some buildings and almost ran in to me. I was nice enough to hold the door for him.
I saw a group streak in the early 70s when I was in college. I didn’t do it, but I did once try to skinny dip at a local beach (I stripped down, but the water was too cold, so I got back out).
People were rarely arrested and if caught, they didn’t get any serious charges. No one considered them sex offenders back then.
I was at that game. It was so cold and I couldn’t believe that somebody would willingly choose to run around without any clothes on.
It was a brief thing in the early seventies at my small college in Virginia. Usually during spring as finals approached and students were just blowing off a little steam. Harmless and a little funny because of how prudish folks were offended.
I suppose this doesn’t count as streaking,but you have to note this chap’s dedication:
I like your username / post combination. Would’ve been even better if you’d admitted to streaking.
I took a quick jog at an outdoor party while waving my pants above my head but that pales beside the fellows who dashed in front of three womens’ dorms with many in attendance.
Cold enough that Jimmy Jones muffed the snap for what would have been a sure game winning FG for the Alouettes too.
In the 70’s streaking was just for streaking, not to bring awareness for some cause or movement. It was purely to bring attention to one’s self or to satisfy some dare from others. While not as prevelant today, but usually at televised sporting events, it’s a mixed bag of motivations, some do it to bring awareness to some sort of cause, whilst usually that cause is ever known or people just don’t care.