They used to be very big and dominated search results for various technical information, before stackoverflow was a thing. It was so infuriating when the only possible clue to your niche bug was an experts-exchange paywall. And that happened a lot for way too long, after it went bankrupt and was bought by venture capitalists.

I'm so very glad they're mostly irrelevant now, they made the early 2000's internet more painful than it needed to be.