In fact, the numbers have been staggering. Over 70% of the Regionals Top 8 decks played Skullclamps in the main deck. Never before has a card dominated Standard to that level. Of course, it helps that this time around it's colorless and only costs one mana. The only requirement? Play creatures, hopefully with one toughness.
The numbers don't seem to be quite that high at this tournament, but only because the metagame has had a little time to adjust. Every deck that doesn't plan to abuse Clamp has a plan to stop it. The breakout card for that strategy? Oxidize. Mono-White and Goblins are both splashing Green thanks to the mana smoothing provided by Windswept Heath and Wooded Foothills. In fact, it seems like it's only thanks to Oxidize that the format has stayed in the slightly reasonable shape it's in now. Interestingly, the words "can't be regenerated" play a large role in the card's success, due to the popularity of Welding Jar in Affinity main decks.
Besides the obvious ramification of everyone either playing Skullclamp or Oxidize, there's another effect that's slightly more subtle. Since so many players are packing large amounts of artifact hate, it's become a terrible idea to run a low number of artifacts in your deck. Essentially, putting four Skullclamps and no other artifacts in your deck means that you're just making sure your opponent will always have a target for his artifact removal. If you go with no artifacts, you're giving your opponent numerous dead cards. If you go with all artifacts, you're planning on overloading his artifact removal which, as you can see from Affinity's consistent results, is a fine plan.
The term "splash damage," which Mike Flores recently coined, comes to mind. The idea is that, even if you're running a deck that isn't expected by most players, you still run into problems when you run cards that are too similar. An example would be building a deck for this format that tries to abuse the synergy of Soul Foundry and Chittering Rats. Almost every time a Soul Foundry hits the table, it will find an Oxidize waiting for it. Did they put the Oxidize in their deck because they were expecting Soul Foundry? No, but that doesn't stop them from wrecking you with it.
There are a few exceptions, of course. Solemn Simulacrum is the perfect card to play in this environment, because you're hardly sad when your opponent spends a card and some mana to remove it. Big Red runs Damping Matrix in the main deck because the card is only there to target Affinity, which generally doesn't have artifact removal. The fact that other decks will remove the Matrix is annoying, but the card wasn't there to fight them anyway.
It seems like most players have come to this conclusion. Goblins, which enjoyed the card advantage from Skullclamp like perhaps none other, has stopped running it for this very reason. Without Skullclamp, it has exactly zero artifacts, although a lot of versions run it in the sideboard to bring in against Wrath effects. Goblin Bidding has all but fallen off the radar.
One deck that does seem to defy this logic is the quietly popular Elf and Nail. Sameer Merchant has popularized this retooled version of Tooth and Nail that mainly just has Skullclamp as the only artifact it cares about. Presumably it uses Skullclamp to keep up with Affinity decks and punishes the slower decks (the ones that can remove Clamp) with its inevitable Tooth and Nail strategy.
I can't wait to see what will happen to the format once Skullclamp leaves. There's been a lot of murmuring about Krark-Clan Ironworks, but without actual tournament results nobody's sure if the card will live up to the hype. In any case, it's time for Skullclamp to retire from the scene. What a strange world it's been, where aggro decks always have a full grip and control decks absolutely have to remove a certain card before they'll have a chance. It was fun for a while, but it's clear the time for change has come.
Rest in peace, Skullclamp.