It's in the amazing, but true category.  In another life I was a pipeline engineer in Ponca City and Lake Charles for a major.  I'll bet you insiders have no idea who THAT is.

Once a sulfur-reducing bacteria colony gets a good toe-hold they create a tough-as-hell shell.  Scraper pigs won't dislodge them in the worst case.  Then the acids that they metabolize burn a very neat hole straight down.  You'd swear that some holes had to have been done with a drill; perfectly circular with clean, straight sides.  These guys are really bad news.

I managed a few smart pig surveys like the ones that I imagine found the corrosion in Alaska.  The technology is was pretty amazing 10 years ago, and it must be Star Wars-like today.  With decent maps and a good odograph (yuk, yuk), we could usually make one backhoe hole to find the corrosion.  And the corrosion was always there.  Although sometimes the anomoly was actually from some very, very lucky backhoe operator sometime in the past who almost had a really bad day.

In another life I was a pipeline engineer in Ponca City and Lake Charles for a major.  I'll bet you insiders have no idea who THAT is.

Heh, heh. I spent two years in Ponca City myself. But I will never, ever move to Lake Charles.

The scale of equipment at CRMT and LCPL were impressive.  Great big pumps that could flat get up and move some oil!

Gotta love zydeco.

Smart Pigs and now Scraper Pigs..
  Sounds like a new John Carpenter movie is in the works..  maybe Jim Cameron.
There's a whole taxonomy:  brush pigs, batch pigs, rescue pigs, de-waxing pigs, de-watering pigs, tow pigs, magnetic cleaning pigs.

You even have to provide the appropriate ecosystem: pig launchers, pig traps, pig signallers, etc.  A pipeline system is much more than just some round steel that you punch a hole through.  Just make sure that OD > ID.

BTW they got their name from the sound they make as they travel the line.

I heard a story from an old oilman to the effect that in the very olden days they actually ran a real live pig (or piglet, depending on size of pipeline) down the pipe to test for obstructions. The pipeline was too narrow for the pig to turn around, and so it could go in only one direction. If the pig got stuck, then you could hear exactly where the problem was and bring the steam shovel to the appropriate location.

True story? I don't know. Does anybody know?

I don't know if that is true but some years ago New Scientist had a small news item about a new instrumented pig that was going to be used in the North Sea and the resident cartoonist decided to illustrate the item with a cartoon showing the four legged sort of pig being put in a pipeline. The magazine was inundated by animal lovers protesting at such cruelty.
No idea.  But I have seen formerly-live chickens that were found in the pig trap.  There were some known malcontents who had motive and opportunity.  Also, wildlife will creep into the open ends of pipelines under construction.  Good work practice is to cap off the ends at the end of the day, but we all know that every best practice is always followed, eh?
Mark Twain story.
The Romans had lead pipelines that carried aquaduct water under pressure down and up a valley to save on building one of those masonry aquaduct bridge things. Pigs might go back farther than you think...
We've seen bacteria corrode stainless steel pipe in nuclear plants.  Different conditions, of course, but those little bugs can go anywhere.