ShareThis, Inc. owns that particular button design (as explained on
http://www.sharethis.com/legal/privacy/usage-guidelines/#sthash.omZ0f3AN.dpbs). Several websites, like YouTube as someone mentioned, use the same symbol stylized differently. The NODE logo does resemble it, but it is slightly different in shape.
In the context of NODE, the logo actually works well, but I can understand why some would want it to be changed.
"Except as discussed in these guidelines, the mark is intended to stand alone and should not be integrated into other logos. So, the mark should not be used as a trademark or service mark, or incorporated as part of a trademark or service mark, in a manner where it is, would be, or could be associated with a particular individual, organization, product, or service, or in any other way that would imply, indicate, or convey to a casual observer, consumer, or otherwise, that the Share Button, widget, toolbar, or other ShareThis product or service was exclusively or primarily associated with a particular individual, company or organization, product, or service not owned or controlled by ShareThis, Inc."