In the context of the three most important questions on should ask when choosing a postdoc, came this:
1) will I get a good letter? The more famous your writer, generally, the better. Yes, this matters.
— Matthew Hahn (@3rdreviewer) December 2, 2015
Ok. I get this. But damn if this isn't bad for science. We complain about the homogeneity of academic science. There are large fields where the Academic Tree of Life looks more like a bush, with a few central hubs (almost always older white men). We complain about science too often being a "who you know" game, despite claims of a meritocracy. And the reason all this is an issue is precisely encapsulated above.
Was your advisor famous enough to turn some heads in a search committee? On a funding panel? Are you one of the chosen, or just someone doing science for people who have to work to get their papers in the upper tier journals?
From the selfish perspective of a student who might benefit from such career advantages, I recognize the utility here. But this kind of thing is as corrosive as the Glam Mag Game. Doing great science and learning new tools (Matt's other two suggestions) should be the most critical pieces of the puzzle. Unfortunately, like the Glam Mag Game, individual decisions and motives drive a behavior that is bad for the overall endeavor.