I think it would be a mistake to get rid of unverified accounts or restrict them. Several people are saying the problem is underaged avatars getting on sl. I've watched my kids play many many games on the internet, on x-box, etc. etc. and at the most, these games require a birthdate, name, address and a credit card of file of the person or a credit card of the parent if the person is under age. Kids on other games can still for the most part put in whatever birthday they want.
Think for a moment about real world consequences of restrictions from a business point of view. If a company started requiring driver's liscenses as someone suggested, it would restrict cash flow and also sig. reduce the number of paying non-griefing customers that are spending money on SL and contributing to the community. In this society, people feel hassled enough by requirements, i.e. airline security and if a company starts requiring i.d. etc. to be on a sim/play a game, many people will say, why bother?
E-mail accounts are so easy to create that linking accounts to e-mail doesn't mean anything. As for any kids that might be coming over to sl, the majority of them aren't "serious" griefers and having watched teen life all summer and being in communication with kids that are playing teen life, I concluded reasons the majority of most kids come over to sl has nothing to do with wanting to grief or having porno, or whatever because they canand do grief over there and since each kid cannot be watched all the time they are on the sim., one kid or the other smuggles enough "adult" contraban into tl to satisfy any kid who wants to do that sort of thing. LL gets rid of it, may ban or suspend the kid and another one recreates. Such is the nature of teenagers. So the reasons I see that most kids come over to sl if they do have less to do with griefingand more to do with the fact that there is much more to do over on the main grid. If you watch kids, playing over on the teen grid, then you can see that it is much smaller and there are many less activities, although there are some good programs that have been started over there. Many of the griefers who have been bothering us when I have been over at the sandbox lately, I found out were of age to early 20's. I only found this out because there was someone there who knew them from rl.
Whereas, if alt/or unverified accounts start being restricted on actual adults, then I believe the population of second life would decrease. Many people use alts/unverified accounts either to do perfectly legal personal activities in which they feel more comfortable with as much animity as possible or because some people just do not want their sl life being connected with their rl in any way. There are quite a few "people" on sl who would not be able to interact with other "people" as much as they are able to in rl for a variety of medical and social reasons.
If you start restricting what unverfied or free accounts can access, then consider that there has to be more programming put in place for that and also SL may suffer the problem that another sim community does, in that they are having problems getting people to join because the "free" accounts are not allowed to do/see enough of the community to make them want to commit any further.
Lastly, I've talked to three software engineers in the past few days and they all agree that the problem has to be fixed on the programming side to make it so griefers cannot cause so much havoc with the system. One software enigneer I spoke to remarked that if these are indeed children causing this problem, which that hasn't been revealed for certain that their security meaures (on the programming side) do need to be fortified because if a child could cause grid wide havoc then imagine what an adult with even more malicious intentions could do.
I assume from what I am reading that that is what LL is trying to do right now, fix the bug that is allowing griefers to corrupt the system. In rl, policies that punish the many for what the few do rarely succeed long term and since there are humans behind the avatars, then that probably holds true for sl also.