Lay off employees until they're profitable.
Tech companies tend to invest ahead of growth, because tech markets tend to be winner-take-all and if the market grows when you don't, somebody else will take the market. They're effectively using their employees as insurance to make sure nobody else can catch them in the market.
As a result, they often have orders of magnitude more employees than is necessary to keep the lights on, the product operational, and the money flowing in (at least in the short term). Google, for example, really just needs datacenter ops technicians and SREs to keep the product up, which is maybe 2% of their current headcount. If they laid everyone else off, they'd eventually become vulnerable to a competitor or lawsuit or public opinion or unhappy/indifferent customers. But until that happened, they could maintain quite hefty profits.
I don't have a stake in Github. I am a user with 2 distinct roles. In one role, I work for a company that pays for Github's services. Github has done a very good job hiring people who have maintained the service as it scaled to very high levels. I am concerned that Microsoft will be unable or even unwilling to keep those teams intact. They may wish to restructure the organisation. They may wish to change middle management in an attempt to make it profitable, etc, etc. Github has had a good track record with us. Organisationally we have no experience with Microsoft, so it's a risk.
Personally, I spent a chunk of my career working in the MS world (working with gold/platinum level partners). This is ancient history by now (10 years ago), but my experience with MS support was abysmal. Essentially "support" amounted to having a telephone number where I could report issues. No follow up allowed. No notification if the issue was ever resolved. Upgrade to the next version when it comes out and check for yourself to see if it has been fixed. Hey, that's why we pay for those MSDN subscriptions! Though, if you have about 1000 seats in your license, you can get real support (if you are lucky). Maybe that's all changed and they are fantastic, but once bitten twice shy as they say.
In my other role as a consumer with Github, I have my personal repositories there. I still vividly remember MS's push to create a division between "hobbyists" and "professional developers". The idea was to provide different levels of access based on the idea that "professional developers" work for large companies that will pay for high licensing fees and extensive support contracts (which only really seem to count if you have at least 1000 seats... see above). "Hobbyists" are intentionally crippled by giving them just enough access to seem like they can do something, but denying them crucial things.
With the release of VSCode, etc, I can see that the company has changed, but old ideas die hard. 10 or 15 years is not enough time for me to feel like I can trust the company. Will they slowly screw me over by using their dominant position to "boil the frog" -- slowly crippling their "hobbyists" without ever doing anything overt enough to cause them to jump out of the pot? Only time will tell, but yes I'm quite concerned. To be fair, MS is not the only potential purchaser who would concern me. At least it isn't Oracle!
GVFS. I believe Github will only deploy to Microsoft's GVFS sometime after acquisition. This is one of the more obvious plans, I thought shrug
What do you think Microsoft would do to harm Github? I doubt it would be as bad as what became of SourceForge.