You can block gift card in most payment gateways, I imagine you could do similar with Apple's system. There also is mixed evidence that Eli Lilly's stock actually went down from the tweet, given it reacted hours after the tweet and never recovered (usually fake news items effecting price will immediately correct back to the previous trading level.) Several articles I read about it bury this deep in the article, basically alluding to "we'll never actually know why the stock went down." It also becomes slightly questionable about if a quant, etc fund would not know the difference between accounts, when you really think about it...it sounds improbable.