To be clear, I'm not worried about my kid getting into college yet, but other people out there much be much closer to the process.
In College Admissions, Athletes Are the Problem - Room for Debate - NYTimes.com: Like it or not, 40 percent of the class at most top colleges are reserved for "hooked" kids -- the largest group is generally recruited athletes (up to 20 percent), the rest are legacies, underrepresented minorities, development cases (donors) and V.I.P.'s (famous people's kids). It's hard for me to say legacy preferences are not fair because the truth is that the process isn't fair and legacies take up a relatively minor percentage of the class (typically 10 percent).
Their boost? Generally only two to four times the general admissions odds. To put this in perspective, for a school that has a 15 percent admission rate, legacies might get in at 35 percent, but recruited athletes are more like 80 percent and minorities closer to 90 percent (at least for African-Americans and native Americans).