I think it's a combination of both. Icahn's investment in Apple was the reason that people found reason to invest, but that information was brought to people th

I think it's a combination of both. Icahn's investment in Apple was the reason that people found reason to invest, but that information was brought to people through the distribution channel of Twitter. So Twitter is an accomplice in this situation, since it acts as how that information got disseminated to an audience, which I think still counts for a lot since it could have been an important signal, but it without Twitter, not as many people might have not known about it. Not only that, but the fast dissemination of this information (due to the nature of Twitter) might have made the stock go up faster than a news article coming out a day later, being read at different times of the day.