Virtual worlds bad for kids?

Virtual Worlds with commercial toy tie-ins may be bad for kids. This seems to be the message by Lord Puttnam in his opening address to the Virtual Worlds Forum in London (which unfortunately I'm not attending). He seems troubled by the ethical implications of virtual worlds designed specifically for small kids.

I seem to be this premise repeated often in debates regarding new technologies. Paraphrasing something I heard at a conference recently (I can't remember who said it), all technologies that come into being before you are 18 years-old are part of the natural order of things. All technologies that come into being when you are between 18-35 can be adopted and learnt. All technologies invented after you are 35 are the work of the devil and must be banned.