The worst part, MegaByte, was that legally Nintendo could not restrict the contest to people who owned the games (it was like when Fox did that Who Shot Mr. Burns contest, they couldn't restrict it to people who watched the show). This meant that if any of the 151 winners didn't own either Red or Blue, they would get something different.
I did manage to get a legit Mew through a online trade in Diamond (the person I got it from had a legit Mew and used the Emerald cloning trick to make copies of all the legendary Pokemon he had and traded them).
I will be happy to get this Mew since I need it in both Platinum and SoulSilver, but the times that Celebi has been legit available have been much rarer (the only times in English were a contest in Nintendo Power with 251 winners, and a 24 city tour in 2006 to celebrate the 10th anniversary of the franchise). As it was already mentioned, the Celebi giveaway also unlocks a secret battle with Giovanni (with storyline revelations) and will unlock something in Black and White. I am just glad they resumed downloads after almost 2 months.