Agreed. I was fairly entrepreneurial in College (at the expense of my grades) and I'm really glad of it. I wish I'd traveled more and done a bit more on the intramural front, but am damn glad I didn't invest the time necessary to get straight As.
If you're actually using that extra time to pursue entrepreneurial activities and you're sure you don't want to attend grad school, then you're probably right. For the vast majority of students, though, I don't think that is the case: much of the time saved by not doing well in class is just squandered doing the typical things college students do. If you're willing to put in the effort, you should have enough time to get As and still do lots of worthwhile extracurricular things (I certainly did, in any case). Also, having good college marks (plus good letters of recommendation from profs) is always a useful backup in case you ever decide you want to go to grad school in the future.
Well, perhaps for the "typical" student, sure -- but by most metrics I would say the YC news audience is atypical. If you have a small amount of natural ability coupled with a work ethic, it is not a matter of getting As or having "something of a social life" -- you can have both.
