I think the trend is reversing. I mean holy shit, look at LeBron.
The problem lies with international players more than anything. People drafting 17 year olds out of Lithuania to play for them in 5 years. That's horse hockey.
High School players are getting the hype right out of the draft, and they are better now than before (LeBron, Melo -- he was a Frosh so that's almost the same thing), so hopefully someone like Howard will do that too. Though he's a big guy, so he's more being drafted for athleticism and size than for skill I'm guessing (i.e. KG, O'Neal)
Basically like what I said, people go for up-side because when KG had Kevin McHale teaching him, he became one of the best players ever. A youngster can learn and learn well. The Pistons should have brought in the Worm to teach Darko

. But in college, it's just... I guess that people leaving early leaves a lot of players floundering, and being forced to play in Canada or Europe. Because they leave too early. And that makes the College teams weaker... which weakens the NCAA stature, which weakens the draft, which makes people not want to go to college players.
You know when Shensher (however it's spelled) goes into the draft, even after 4-5 years, he will be a top 10 pick. Polished and big. That's all that matters anymore. But if you're 6'5" and polished, you're almost useless. When KG can guard you, you better be 300 pounds or 7' tall or both.
But anyway yeah, high school players can make a difference more, because 1) confidence 2) HS programs are becoming like college programs with recruiting out of grade school, and the money they put into the programs... 3) having something to prove and 4) the college graduate rookies are not as good as they once were. Just think about it. The "good" HSers who come out now are the same people who would be "all star" collegiate athletes out of the gate in 4 years. So you're right in that... they're weakening the college ranks by doing that, but after a while, it will balance out. The talent coming out from HS will be the ones worthy of coming out, and the rest will go to college. I HOPE.