Let me see if I can help out. I live in San Francisco, and have been to several community meetings on this issue.
Usually when people talk about gentrification, we're talking about a single neighborhood, or a few neighborhoods. What we're seeing here is happening across the entire Bay Area, with rents rising at an astonishing rate, along with evictions (up 38% since 2010), primarily Ellis Act evictions (up 170% since 2010), at least in San Francisco. Even with rent-controlled apartments, Ellis Act evictions are allowed by the state, and allow apartments to be taken off the market and converted to condos, or other models where the unit is essentially "sold" and taken off the rental market. We've had some cases of people, especially the elderly, committing suicide because they're about to be evicted from their apartments that they've had for decades. Home prices also rose 22% during the same period, but I don't know of anyone rich enough to actually buy a home here- the name of the game in SF is renting, and the latest vacancy rate in San Francisco is somewhere around 2%.
There are several other complaints, for example, many employees commute to Silicon Valley, and their employers use fleets of huge private buses to get them there. These buses use city bus stops, in some cases making it impossible for other citizens to use the city bus stops as intended. This has resulted in some protests and altercations that have made the national news lately. To add insult to injury, we have many people in our city government, especially our mayor, who have made major concessions to some tech companies, like Twitter (to keep them in the city after they threatened to leave). These concessions have cost the city millions in tax revenue.
As Harvey Milk explained back in the 1970s (most people don't know that he actually had to move out of his famous camera store when his landlord raised his rent over 300% due to this same kind of speculation), this kind of boom raises rents, which lowers disposable income for everyone, which reduces the income for local businesses, and the whole thing just ripples across the area, destroying everything.
I'm a software engineer, and I've lived in the city for about seven years, so I moved here before the current boom. But I'm older, and at 50 I find it's almost impossible to find a job with any of these companies. They have a "monoculture", where you have to be young, and it helps if you're white and male. I know this might make me sound bitter, but I've found that many tech recruiters agree with me, that many of these companies don't care about profit, so they don't care about producing results, what they really want is someone to party with including drinking during work hours, going out every night after, etc., and then flipping the company as fast as possible- they don't want someone old enough to be their dad around. I survive by freelancing, where people only care about results, and my clients don't live in the Bay Area.
This monoculture is dramatically altering the city. What we have is a huge influx of young people that in many cases are getting starting salaries of over 100K immediately out of college. Mostly they're white, and in many cases they have absolutely no interest in politics at all, and especially politics in SF. It's like having a gold rush, where almost all of the miners are rich, young, and white- it changes the flavor of the city, and pushes everyone that was there before, except those that are also rich, out of the city. You might have heard about some arrogance in the tech sector, and I believe that part of the problem is because of this monoculture. So many problems could be avoided if they employed some older, more experienced workers or workers that weren't all young, rich, white, and usually male, so that they could get other perspectives. Instead, they insists on relearning everything the hard way, using bleeding-edge technologies so they can put them on their resumes before they move on in a few months, and unfortunately, usually all of this is playing around with your data.
I've edited this to add that I do love being around young people, indeed, I worked at major research universities for most of my career. The problem comes from having a single demographic flooding in and the associated land speculation, wiping away everything that was here before.