#4 is a tough one. I don't think this is only true of startups. To some degree it happens everywhere. Anecdotally I have seen a relatively large swath of technical teams in my years consulting. Most teams are not diverse and I have seen some interesting cultures develop. Most managers will hire people that they like on some level. Its just the nature of people. If a hiring manager doesn't like you you probably wont get the job unless you have a niche skill that justifies him putting up with not liking you. I don't think it is good or bad, but generally just the way things are. One place(a large oil and gas pipeline) I consulted had a manager who ruled with an iron fist and over the course of about 5-6 years(which was the average tenure of the team) the team evolved into a group of very passive people. I actually know someone who left that team after 6 months because he couldn't deal with the managers style. However the 7 people who did were happily there and that team was not very diverse: all 40-ish year old males from India.(I am not making the implication that East Asian males are passive. Just this team of them was as the managers style curated that)