Legal & Ethical Questions in the PC Audio Age

I haven't ripped my entire CD collection yet, but I probably will in the near future. And I'll continue to buy CDs until I can download them in Redbook or better quality. I'm wondering about the legal and ethical implications of disposing of physical CDs once I've ripped them.

(I appreciate the value of keeping them around for archival purposes, but let's suppose that I'll want to get rid of some of them.)