You see a couple of ads mixed in your feed; behind that there's a big machine selling that space to advertisers and mixing it into the timeline of every user based on whatever profile Twitter has created for you. Then the advertisers want to know how their ads are doing, or they'll stop buying them…and you'll probably need to have salespeople to get them to put money into your ad system in the first place.

> I guess you could count the god-awful default feed ordering as "recommendations", but there is nothing advanced about it.

Just because you don't like the ordering doesn't mean it's not advanced.

> I am not sure why there is so pushback against the idea most companies are overstaffed.

Twitter could be overstaffed. In fact it probably was overstaffed. But it's not overstaffed in the tune of of "it should be 10 people working out of a garage".