Turns out that the move of Buffy the Vampire Slayer from The WB to UPN may have been the catalyst that set both networks on the road to their eventual merger.
On one had, while financially a good move for The WB — they didn’t have to pay the huge licensing fees to Fox, who produced it — it was an apocalyptically bad move for the network’s brand, which had built youth-oriented programming around the audience that gathered around Buffy and other shows built around snarky post-everything teens. And we all know what happens when long-term brand identity is sacrificied for short-term financial gain.
At the same time, it may have saved UPN, or at least turned it into the walking dead, and like most zombies the UPN went in search of brains, but unfortunately, they only found models. So they essentially went after The WB’s demographic, which resulted in Veronica Mars — yay — and enough money-drainage for them to pack everything in and form The CW, about which the jury is still very out.