I can understand it when it's about David Cameron paying tribute to M. Thatcher in parliament, before any other MPs get up to say something about her. That definitely has an element of "leading" and "officialdom" about it. But a tweet or a facebook comment? Why does Irvine Welsh get to lead tributes, and not the man's wife / mother / business partner?
When I do a search of the term on the Guardian Website, more often than it just seems to mean "is a famous person".
"Authors including Patricia Cornwell and Ian Rankin have led tributes to PD James, the crime writer who died on Thursday aged 94."
"Sir Lenny Henry has led tributes to the actor Larrington Walker, who died at the weekend aged 70."
"Actor and musician Goldie has led tributes to “gifted” vocalist Diane Charlemagne following her death at the age of 51."