I have given the side eye to all of the "Shop right in the app!" functionalities that have rolled out in the past year although I'm the first to admit that I'm not the type of person to randomly want to buy things that are slapped up on my newsfeed. I purchase probably 90-95% of my online stuff from Amazon and cannot see anything changing that, especially when I can go to Amazon, look at tons of reviews (and I read the reviews on everything before buying, whether it's $15 or $1500), buy with 1 click, know it's going to be at my house in less than 48 hours, and know that there's a rock-solid return policy that goes along with it.
I don't see the advantage of shopping from Twitter or FB or Pinterest, although again I'm not exactly their target demographic. Are they hoping to prey on teenagers and bored housewives with too much money to burn?