This tangent is in relation to my shuttering one forum.

That forum was around a music band in the UK, and the audience of the forum turned out to be lower than expected - University age. They were emotionally immature, over-shared online, slept with each other, had relationships and break-ups... all in public. The music forum did have lots of music info on it, but it was intertwined with a lot of very highly personal information posted at a time when a reasonable expectation of the internet was ephemerality.

It was totally right to protect the individuals future selves from their past selves, and I would delete again.

There are certainly downsides to hording data. At the very least, information takes up space. It also tends to suck up mental bandwidth: you have to keep organizing, de-duplicating, and migrating to newer formats. It's much easier to just delete it. Just like it's much easier to throw old ratty tshirts. IMO, data hoarding is just as much of a mental disorder as hoarding physical stuff.

This idea that all information must be preserved for forever is also at odds with privacy. See, e.g., the right to be forgotten.