As research had indicated that people were wary of signing over their credit card number in order to gain a free basic account, Linden Lab has made changes to the registration procedure in order to allow people to sign up for a basic account without anything other than an assertion of their age.
Experience has shown that people were far more likely to come in world and set up a new account if they weren't asked for financial information.
There has been a big increase in registrations, plus the usual philosophizing on the SL forums that the end of the world is nigh. Two big related questions which are avidly discussed, are the much higher chances that there will be underage players on the main grid, rather than on the teen grid, which is separate; and the likelihood that - as Surreal Farber postulated - we are going to be ass-deep in alts.
Alt characters are alternative avatars which someone already established in SL uses for a variety of reasons. Some people have a professional avatar who builds, scripts, or holds events, and a private avatar who is for fun. Some do it the other way around, and are well-known in their main avatar, and have a secret scripting avatar who is deliberately a Nobby No-mates in order for them to be able to script away in peace.
Once upon a time, when accounts were tied to credit cards, each credit card was limited to five, latterly three, accounts. Now that financial information has been separated, that limit has gone. It will be interesting to see how this affects the number of accounts which have been active in the previous 60 days, which is one of the new statistics provided on the website.