I wouldn't give too much about random people asking for investment advise and saying they are buying Alt Coin X on Twitter. People can say anything just to become famous for a day. In my opinion people who promote their trades like this on social media, are either looking for re-tweets or might be already owning the specific coin and are looking for more investors. It could be that they are just promoting their own positions, so they could sell in the future. Tweets like this will hype the crypto market more and promote fake beliefs that you get rich overnight without taking too many risks. We need to be aware that there is a lot of risk involved in trading cryptos.