Science magazine has an article in its "careers" section about the job prospects for the hundreds of young physicists who worked on the Large Hadron Collider: "After the LHC, the Deluge".
The numbers make the problem clear. In 2007, the year before CERN first powered up the LHC, the lab produced 142 master's and Ph.D. theses, according to the lab's document server. Last year it produced 327. (Fermilab chipped in 54.) The two largest particle detectors fed by the LHC, the A Toroidal LHC Apparatus (ATLAS) and the Compact Muon Solenoid (CMS)—which both independently spotted the Higgs—boast teams of 3000 and 2700 physicists. By themselves, the CMS and ATLAS teams minted at least 174 Ph.D.s last year. That abundance seems unlikely to vanish anytime soon, as last year ATLAS had 1000 grad students and CMS had 900.
Big Science works well when it produces huge rafts of data that allow many independent groups to do interesting work. It works poorly when it hogs resources toward expensive projects that can only test a handful of hypotheses. Nothing wrong with being a cog in a machine with 3000 cogs, but you have to be a shiny cog indeed to build a long career out of a project that will eventually close:
Today's mega-experiments rely on armies of graduate students and postdocs to do the nuts and bolts work, Asaadi says. That's fine, he says, so long as everybody understands the situation from the beginning. "When you're starting graduate school, is your advisor telling you, 'Look, you get this great skill set that will be transferable to other things outside of academic physics'?" Asaadi says. "Or are you being told, 'Just work hard and there will be something or other [in physics] in the end'? It seems like it's more of the latter." He adds, "This is where we got some pushback from advisors—it was seen as whining."
From a 2008 report by the American Academy of Arts and Sciences: "The average newly minted doctorate will not receive her or his first NSF award until age 39 to 40, with the median age 37 to 38."
This number has been getting higher over time, but since the current value equates to the average year 4 or 5 in a tenure-track position (after a postdoc), there is probably no room for it to increase -- this is very much the age at which people must either have a way make it in academics without a federal grant, or leave.