I can't imagine Hitchens performing Communion or Russell leading a
prayer. If they did, they would seemingly lose all credibility.
I feel compelled to ask, what has credibility got to do with atheism or faith? Why should an atheist be considered more or less credible than someone who believes in a deity? If someone is a priest, yet philosophized the non-existence of God, would it hold that he were necessarily a hypocrite, or merely exploring another point of view and questioning his faith? If someone is a self-proclaimed atheist in public, but secretly prays to God, is he necessarily a hypocrite, or is he someone who is questioning his atheism - in some ways his faith?
In both cases, you could say that neither is strictly practicing what they preach, and yet it doesn't necessarily follow that they lack credibility if your own beliefs align with theirs. The Christian may say that the Atheist lacks credibility because history documents through scripture that God exists, and the evidence is irrefutable to those willing to see it. The Atheist likewise says that there is no fundamental basis for the existence of a supreme being and the evidence is irrefutable because there is no directly observable proof.
As to whether anything has changed, do we have any knowledge that confirms that ancient philosophers weren't vilified for an apparent hypocrisy? We do know that many were persecuted in their day for teaching heresies, so outwardly practicing hypocrisy would have been a means of survival, but not necessarily an indication that the philosophers themselves were actually hypocritical.
Is it any more necessary today to practice what you preach? Today we have technologies undreamed of in ancient times. I think that makes it so much harder for anyone today to preach one way, yet live another. In ancient times, your reputation could not be disproved merely on hearsay unless you had a particularly vocal and powerful opponent. These days, any kid with a smartphone can be your undoing. In some ways, it is therefore more important to practice what you preach. However, the general public can be quite forgiving. Give it a few years, and people will forget an indiscretion or two. Do some amazing good in the mean time, and they'll forgive you as well.
The cynic within me also feels compelled to point out that with good PR, even the most vilified individuals are likely to be portrayed positively enough that the odd hypocritical moment will be overlooked. Those who live a hypocritical daily existence however, are likely to be treated rather harshly, yet like those philosophers of old, each will have a loyal core following who will see past the practice in order to accept the preach. In that sense, perhaps things haven't really changed at all.