On Feb 1, 2021:
I lurk here from time to time, and the whole GME thing has me a bit fired up because 99% of everyone talking about this are turning it into a righteous narrative of 'hedge funds bad' and 'look at what Robinhood did, the system is rigged!' Not saying I know everything, this is just my understanding (and I'm sure could be off about some things).
Long story short on the Robinhood scenario: the broker doesn't actually obtain stock with your money, even if you're not trading on margin (e.g. with your own cash).
The broker puts up money (collateral -- usually a few percent of the notional value of the transaction) to the clearing firm while the transaction clears (2 days). The volatility spike of GME caused that collateral requirement to go up to 100%. Any broker using Apex clearing put the same restrictions on buying GME (and whatever other ticker symbols that were in that group). Robinhood used to use Apex, but I think they are partially self clearing now.
Larger more well capitalized brokers (like Fidelity) did not restrict trading because, well, they could afford it. If you watch the interview with Vlad Tenev (Robinhood CEO), he basically said this, but did an absolutely terrible job of it. I can see why he gave such a response though -- the alternative was to say "we're too broke for this." I do wonder if he thought "hmm, this might look bad given our conflict of interest with Citadel". On the other hand, the CEO of WeBull explained very well IMO what the situation was.
IMO this is a must watch: https://www.youtube.com/watch?v=v2O6lXZ4rkI.
As for the whole 'hedge funds are getting f---ed right now': I don't know what to think about that. Of course, there are losses, and yeah the short float is over 100%, but the daily traded volume over the last week has sometimes been multiples of the entire short float (referencing the video above and it's easily verifiable on yahoo finance for example). As it's put in the video I linked above, a squeeze would really only happen if there is not enough volume in a day for short positions to be unloaded. This makes sense to me. Not only that, but it is possible to hold a short position as part of a larger neutral strategy...google statistical arbitrage or dynamic (delta) hedging. The short float hasn't really decreased at all, it's still astronomically high.