One other note.... Back in the days when players first started, there were no checklists, scrye and whatnot which depicted what was Rare, Unc, or Common.... So, I can remember trading commons for rares and vice versa because we only cared what the cards did at that point... It wasn't until we found singles and scrye that rarity mattered. I had 4 CS very early on, having traded for them among friends who had all bought a starter or two and a few boosters.
It didn't suck that we played MP ante the first time I played and I won like 20 cards... which was a ton considering I only had a starter and some boosters and basically played with all of the cards. The only rares I recall owning at first were Bayou and Roc of Kher Ridges... Those were the days, when magic was really fun and new, when you opened a pack and had no Idea what the cards were until you'd read them and tested them out. Now, with spoiler lists and rarity symbols, it's lost a bit of it's **magic**.
Oh, and for the record, Ice Age was the first place CS was a common, and 4th was the first base set I believe with it Common. If it was rare, I don't think it would have seen any of the limited sets, and wouldn't nearly be as prominent as it is. Does Everybody have 4 Birds? I have 3, and while I don't buy base sets (and haven't since 5th) I've never traded one away, and I've been playing since '94. If CS were the same, I don't think you'd see 4 in every blue deck. It is really one of the most powerful cards, two mana to stop one, or more cards (like an early ritual for a vampire, or any number of cards which require sacrifice to cast). Boomerang is a common and should be, but CS should have been a rare imho and been restrictedto base sets. The inefficient counters are fine as commons(spell blast, power sink - even in it's weakened modern form where it can be responded to with instants).
