I guess the answer is No for any frame built in the last 10 years or so, as it takes a long time to loose enough material to cause weakness. However I have a 60 and a 35 year old road frames, and I can hear stuff tinkling down the tubes when I turn the bikes upside down. I presume the stuff is rust, rather than decades worth of dead woodlice which might have crawled in.

Am I likely to land in a crumpled mess after hitting the next pot hole and the frame snaps in two? Both have been recently resprayed so outwardly look brand new, but I worry about their internal structure, particularly on long fast descents!

I’ve seen frames that have been stripped of paint to reveal holes where it’s rusted to the point that the paint was all that was left. They still hadn’t failed.

Give em a good spray with JP Weigle frame saver. Meant to neutralise any rust in the tubes, and stop any new stuff forming.

I had a 1970’s viscount aerospace frame that rusted through at the bottombracket/seat tube junction whilst riding- a nasty experience as There was an almighty crack and the handling went to hell. I was travelling downhill at the time. Managed to stop but had to walk home. It was 30 years ago though. Entirely my fault as it was my hack bike and salty water from a couple of winters road riding had got down the open ended seat post and accumulated and rusted through from the inside.
Edit:
Looks like they had a known weakness in the bb/set tube area:
http://sheldonbrown.com/lambert.html

Try drilling some water drain holes under the bottom bracket and squirt some waxoyl into the tubes. I had a frame rust through at the seat tube to bottom bracket junction as the seat tube used to let water in at the seat post clamp. That frame was 25 or so years old and is only good for the turbo trainer now.

my bontrager race has a few holes in the seat tube, first used in 1996

My old carrera had some serious scars but other than the drain holes being a bit bigger than they used to be, it’s still sound… I don’t think there’s much metal left around the seatstay bridge though! Mind you, 20 years of neglect.