For some context on the early days of steam, I remember the Friends network having reliability issues presumably due to scaling as everyone adopted steam.

But by reliability issues I don't mean it occasionally failed. It did, but that was early on. I assume they just killed the backend and never pushed a client update to remove it because I remember what was at least months if not a full year of the friends UI just saying it failed to connect to the Friends network.

The actual matchmaking never had any real issues that I remember, but the login servers definitely did, and deleting clientregistry.blob and restarting steam was just a routine thing you did to get steam working again.

None of this is really that surprising though, steam was originally a tool just for beta testers, while the live game used WON for matchmaking. WON was shutting down and Valve had to rush steams public release.