[fecak]

That does make sense. The thing is, that 'minimal acceptable treatment' for all applicants for an internship, which could be in the thousands, is much more costly than for the 20-50 applicants for a more senior position.

When I post jobs, I try to reply to all moderately qualified applicants. And sometimes I'll get an applicant with no industry experience or education who applies to a senior dev spot. Should I spend the time to write a detailed reply to someone who is entirely unqualified and clearly just sent their résumé indiscriminately to my ads (sometimes more than once)? I don't feel obliged to respond to people that are clearly wasting everyone's time.

This is not the case here, and in a perfect world every applicant is flown in, wined and dined, and given a full battery of interviews - but that isn't realistic. Somewhere between an automated response and the wine and dine is the appropriate response. A respectful rejection for two candidates is a small investment, but for thousands it may be unfair to expect.

If you want an example of this, send a wedding invitation to the president. You'll get a reply saying he can't attend and wishes you the best, and it's signed (not by his hand). I'm sure he'd love to give every American the decency of a handwritten and personalized response ("Sorry, in London that day"), but for an American citizen to expect that reply is not realistic.