The question the OP asks is: will having social buttons (unless carefully crafted, non-privacy-threatening, possibly two-clicks-needed) gather a wider audience or just empty the current (and really loyal [*]) audience? Can you win readers by having these features FASTER than you'll lose readers? Are new, socialized readers as well prepared to the high-quality content as the old, antisocialized ones?
Mind you, I have a small LWN-prepared audience on twitter and G+ and I would like a simple way to share with them some of the articles and the discussions I have here. And I think some of them could change into subscribers also. But I would only opt in for a simplified sharing (simpler than right-click on [Link] link, copy link, change tabs, middle-click?) if I could do it without pesky track-all-I-read cookies.