Having a buy button on twitter could be effective or noneffective. Recently on an article in the New York Times. Twitter was having in its mind since two years. After two years of testing, twitter has decided to launch buy button this year. People are more likely to be on social media every day. Even though if they doesn't have time to online shop, buy button can help them to buy from social media.
I think if twitter gets success by launching buy button than other social media, especially Facebook will follow its path. According to Vindu Goel, mentioned in his article that “We have gone from testing this with hundreds of merchants to millions of merchants,” Nathan Hubbard, Twitter’s head of commerce, said in an interview. “It’s built into the software that they use every day to manage their business” This will help twitter to make more money from those companies, the companies chose to sell their products on twitter site. Twitter has around 316 million users in the world and this buy button will become famous within a few days.
Vindu Goel also mentioned about Facebooks idea on this buy button thing that, "Sheryl Sandberg, the company’s chief operating officer, said that Facebook studied the behavior of its 1.5 billion users and concluded that buy buttons should not be a high priority right now." I think Facebook is now focusing on its recent topic " Dislike Button". In future it might have it on its site.