Outgoing NBC head Bob Wright lays out the particulars in an interview with Fortune's Tim Arango. It was 1994 and as Wright explains it, he thought the deal was pretty much done. But then-Disney CEO Michael Eisner slept on the proposed sale and changed his mind the next morning. (Disney eventually got ABC.) On another occasion NBC was almost sold to Paramount Pictures, but Paramount head Martin Davis wound up selling the studio to Viacom instead. As for NBC parent GE deciding not to go after DreamWorks - much to the chagrin of DreamWorks co-founder David Geffen - Wright said "it was a disappointment to me."
There was investor pushback at GE, because they just saw rich guys getting richer who were going to sell us poor guys in suits a very expensive property that probably wouldn't work. But having said that, we went ahead and tried to do it. We reached an agreement relatively quickly with the DreamWorks principals, with Geffen being the principal person in the negotiating. The problem was, there was still hesitation here at GE. We had to hold off on entering into an agreement. I think David Geffen thought this was some sort of scheme to wear them down. So I gave them the right to go and negotiate freely with other parties.
By the way, Wright said he wouldn't be surprised if NBC Universal is sold off in the next three to five years, possibly to Time Warner.