It was always to some extent, but the feed was a lot more formal IMO at the beginning. Content was more like actual articles and links.

But I think users just love / gravitate towards a more facebook style feed.

Part of that might be the "reward for spamming" - any "social media" site is always amazing at the beginning, because only the die-hards know about it and the spammers have no return on investment.

LinkedIn has slightly different style of spammer, but it's basically the end game for anything.