We saw lots of social media news this week, including American Express’ #hashtag purchasing, Donna Karan Twitter and the psychology behind the selfie. Read all about these stories and more in this week’s link roundup. Cheers!

Core Competency Dead: Lessons From Nike, Apple, Netflix, Fast Company. I love this kind of thinking. What's next? How can we leverage the brand for more — new category, a new relevancy into the consumer's life.  This is cool stuff. – Scott

American Express launches #Hashtag purchasing, PSFK. I’ve been monitoring this story since the rumors first started rumbling, and have been excited to see how it unfolds for both Twitter and Amex. In case you missed the news, you can now use your Amex to make purchases just by tweeting special hashtags. If all goes well, this could prove a huge moneymaker for Twitter, and put Amex years ahead of its competition on social. I haven’t purchased anything yet, but I’ve got my Amex synced and ready to give it a try. What do you think? Would you purchase with a tweet? – Matthew

30 Terrible Pieces of Social Media Advice You Should Ignore, HubSpot. Sometimes the best way to learn how to do things right is to see all the ways they can go wrong. For instance, #HaveYouEver found yourself #annoyed by #waytoomany #hashtags in a #tweet? (Don't do that!) This is a pretty definitive list. – Paul

The 25 Most Amazingly Timed Photos, Picstache. I’m taking a bit of a different approach this week and looking at pictures rather than words. Picstache is a pretty cool site in itself, letting people share images and encouraging others to vote on them. Some of the resulting lists of photos are pretty hysterical. But, one of the lists that recently posted shows some impressively timed images, capturing moments that you would have never thought possible. If this doesn’t make you want to purchase a new camera, I don’t know what will! – Annie

Donna Karan Twitter, Mashable. Social media is changing how we interact and now where we purchase. During New York Fashon Week designer Donna Karan team up with American Express for the sale of a charity bracelet sold exclusively on Twitter. This is one of the first items sold on the new Amex Sync platform but certainly won't be last. How big of purchase would you make using Twitter? – Brooke

Senator’s Water Break Battered on Twitter as Brand Misses, PRSA. Social media success means engaging. Every. Single. Day. Brands can’t let an opportunity like this go to waste. – Dan

The Social Psychology of the Selfie, Mashable. Everyone has seen a selfie, and is probably guilty of taking at least one at some point in their life, but why do so many people share these photos? This article delves into the reasoning and meaning behind this trend -- I know I will never view a self-taken photo the same way! Pretty interesting if you ask me. – Chelsey