From what I've found, you really need at least 5 or 6 basics if you want to be able to deal with Crucible of Worlds. Anything less than that and it tends to lock you down for too long and your opponent just pulls too far ahead.
I'd certainly agree 100% with that, and it's why I'm not sitting back touting that it's not an issue at all. Back to Basics and Blood Moon aren't problems... Crucible of Worlds, on the other hand, certainly can be devistating. Basically, either you run a lot of basics (being 5-6+) or you hope you can counter/Duress the little bastard before it hits the playing field. While Crucible may not, in and of itself, win games all the time it certainly has taken more then its fair share, and the tempo advantage it can create had claimed a rather large pile of victims itself.
I played four basic islands at Ontario Vintage. Had I not , Crucibles would have locked me down. Every deck I played had them and I don't play with them. I lost only one match all day and that was because of an active Library. Never drew any Wastes of my own.
On another note I find that five fetches in a u/g deck is just about perfect if you use Brainstorms and Sylvans.
I wonder why Sylvan is not used in these builds more as it really functions well with Brainstorm to ensure good draws if use fetches.
Actually, Sylvan Libary is still used... Just not as openly as you might think. As I mentioned earlier, I use Green instead of Red, and a Sylvan takes the slot of my 4th Brainstorm in 4CC. This being the case, I can attest to the fact that not only is it insane with fetchlands (with or without a Crucible of your own in play), but that morphing up an Angel with Sylvan in play invokes card scooping with lightning speed.
EDIT: Sorry about the double post, could a friendly Mod merge these, please? =PThe "Edit" button on the top right of your posts is your friend

-- Toad