This is an excellent question that I've often pondered and never seen a great answer to.
Do social share/social link icons dilute page juice that would normally go to your subpages. Google could kill facebook so fast if true...Cutts just has to answer a random question about this...say yes to a degree a facebook link would divert attention/importance away from subpages...and wala...webmasters stop linking to them (because it is bad SEO) and facebook crashes.
As is now...the popular sentiment is that linking to facebook, twitter, pinterest, etc...is the silver bullet to making your site rank better in google, but I have yet to see a well thought out argument explaining why.
Certainly it adds to screen clutter and pushes down your content from the most valuable top portion of the screen.
I hope google clarifies how these social media icons influence rankings one of these days...