Not particularly - I mean if they're invested in the stocks affected then they have the opportunity to sell at a profit or just leave them and they'll probably fall back down to the sort of price range they were in before fairly soon.
Perhaps some pension fund has allocated a small % to one of the hedge funds affected but that's an obvious risk.
If you're rich enough to invest in the affected hedge fund(s) directly then you're rich enough to take a hit if your fund blows up.
re: leverage - no not generally spreadbetting, it's mostly US retail traders and spreadbetting firms/bucket shops have been illegal in the UK for about 100 years now.
Brokers offer leverage directly on US stocks, not massive amounts, say 4:1, you're borrowing money to buy stocks essentially, likewise if you short you borrow stocks and pay a fee to do that too.
The bigger impact perhaps (as mentioned above) is options, a call option is the right but not obligation to buy some stock at a given price (strike price) in the future - if a bunch of people buy options then the person selling them those options will tend to hedge using the underlying instrument... so this causes a bunch of market makers to buy the stock and send the price higher. Out of the money options are those where the strike price is higher than the current market price (so you're buying the right to buy at a higher price than you can currently buy now) these options are cheaper (and get cheaper as you move away from the current price) but if you've bought a bunch of these cheaply and the price moves up they become rather valuable and the person holding the other side of that trade needs to hedge more.... ergo buys more stock... and in doing so the price can go up further and so on... so when these "autists" have bought a **** ton of options at different strikes and the price goes up then the market makers need to buy more actual shares and the price goes up further... and better still the people with shorts see their positon go further and further against them and some of them need to close their position, which they do by.... erm buying more stock and sending the price even higher!