I find a good solution is to create a test site for things like this, you can add as many as you like then, test what you like and what you feel might meet current and future customers needs based upon that experience.
As already sort of mentioned, I see a lot of sites that are way too clumsy and bogged down with unnecessary add-ons which not only slow down the page load time (the facebook add-on is a prime example), but just make it harder to navigate
The ultimate goal is to sell products, not to win awards for how many add-ons you can put on one site (or send them off to facebook where you have basically lost a sale whilst they update their mates on what they are having for lunch), a customer doesn't really care at the end of the day what you do, so long as they can enter the site, eaisly find what they want and make a purchase without having to learn just what you were thinking when designing the shop.