The title is so illusory! I'm not talking about your friendship, it's about your friends in the business. I've started a lot of businesses with my friends and none of them have been succeeded. Although there are exceptions in the world and everybody knows them. Business friends are so different from friends. You can end up a business friendship in order to keep your business alive but you cannot end up your friendship just for a business. No word of a lie, I've experienced both of the friendships. There is a nice quote by John D. Rockefeller about this subject which is: "A friendship founded on business is better than a business founded on friendship."
I believe that all the factors of a business such as founders, workers or owners could be and should be replaced by merit in the case of necessity. We have to face the fact that, not all the people are always like a cannonball! As time goes, Some people lose their enthusiasm but it worth to mention again that there are some exceptions! In the case of facing with unqualified people in your business, In order to save the business, you should replace them with eligible people. You can deal easier with the friends founded in business than your social friends. When the thought of a business crosses in my mind, I don't count on my friends anymore. My friends will be forever as a friend and don't want to lose them for the sake of starting a new business as the possibility of losing your friends in business is likely more and more.
As a software consultant in lots of private companies, I've considered this subject a lot. Think about the business you are going to embark on and find your business friends, colleagues, and association based on that.