Most of them are worthless; of any given intern class at a first tier technology company (e.g., Apple), only ~1-5% will actually be offered a full time job. I

Most of them are worthless; of any given intern class at a first tier technology company (e.g., Apple), only ~1-5% will actually be offered a full time job. I really doubt this number. Rehire rates are an important consideration for college students, and they talk. An offer rate below 50% would be damaging. That said, a lot of people find better offers elsewhere, but no tech company is going to no-offer 90% of its interns and keep its reputation intact.