DukeofDuke said:
... why is it that it seems most departments are packed with their own alumni?
Are you talking graduate programs here, or faculty positions? I think if you really look at stats, most departments are not "packed" with their own alumni at either level. What they are packed with is people that have comparable degrees or better, and I'll explain why:
Sometimes graduate programs will admit their own undergrads if the undergrads aim too high and do not get accepted at the graduate schools to which they apply. However, the admissions committee that I was on (that University of Colorado at Boulder), did not do so. I personally know of many cases where we denied admission to undergrads from the institution as well as individuals who did REU experiences at the institution. I think this would be typical of most "top-tier" universities (those with high-profile areas of speciality like Boulder, or brand-name recognition like CalTech -- where you do tend to get applications from all the superstars interested in that research area or that brand name). Often these universities do admit students with high GRE's and interesting research experience from other, smaller universities... although you have to stand out as a superstar perhaps a bit more than if you come from a comparable university (where you still have to be "very good" -- aka. do substantial research work and have excellent performance).
It's a similar case when seeking a faculty position. To get a faculty position at a top-tier university, you pretty much
must be a research superstar. That COULD happen at any university, if you get lucky in your research... though it's probably more likely to happen if you're at a place already known for that level work. But direct hires from the graduate degree to faculty position do not typically happen -- you have to have a good post-doc or two somewhere else and prove your "superstarness". Perhaps you'd have the advantage of connections (being more likely to therefore postdoc in a good lab)... but you still have to continue to be a superstar in that lab -- and even up until you get tenure in your own lab.
The question is... how many people can hold up that superstarness for that long? I'd imagine not many (there's luck required in the lab, as well as dealing with other things that might crop up and impede things... say like family-concerns of various types).
So what I'm hitting at here:
A) You need to be a "superstar" (or nearly one) to get accepted at or hired at a university that is above the "ranking" of the university you've attended.
B) You need to be very, very good (at least "almost a superstar") at your present "ranking" to get accepted at or hired at a university that is at the "ranking" of the university you've attended.
C) It's much easier to get accepted at or hired at a university that is below the "ranking" of the university you've attended.
After all, there are only a few departments that are "top" in certain research areas... a bunch that are middling, and tons that are weak or have no substantial research in that area... or even no research at all (community colleges or many undergraduate colleges that you've probably never even heard of that may be private and religious, etc... and may offer a few physics classes, but not offer a degree).
It's OK to aim high... but what I state above is what I honestly see as the reality of the academic situation -- and it's across fields, not just in physics. It's okay to be motivated... but don't get too disappointed if things don't work out. It's very hard to be a superstar... although they are out there, they are few and far between. So I think people are just noting that if you aren't one of them, you need to gradually accept yourself and learn to work with what you've got. Happiness can be found there. Don't waste your energy on resentfulness (which is, btw, what seems to be implied in the selected quote from your post).
