In a recently published article we have addressed several issues regarding unique author identification. e-letter in Science magazine online We hope that the discussion will go on in order to increase public awareness to this urging problem to a level to motivate an independent organization (NCBI/CrossRef, why not PLOS?) to take the lead to establish a database of unique author identifiers. The multiple advantages of such a database as outlined in an increasing number of articles is just overwhelming.

With regards to your specific questions:
Ad 1) The unique author identifier should be as simple as possible and should not represent "other information". "Other information" should only be linked to it since it is likely subject to change. Therefore, a unique author identifier containing "other information" would inherently not remain unique (or at least not adequate). Furthermore, contrary to E Joly's suggestion as a correspondence in PLoS Medicine I believe that the unique identifier should represent an abstract alphanumeric string rather than including parts of the name or year of first publication as the identifier is meant to be independent of the name. Seniority of an author could be part of the linked information.
Ad 2) I believe that systems exist that are safe enough to protect each author's database entries. Each individual author is free to link as much information to the identifier she/he likes and trusts. A point to consider would be to show the e-mail address (as part of the linked information) in a way that cannot be recognized by search algorithms that scan for e-mail addresses to avoid unnecessary promotion of spam mails.
Indeed, author information needs to be verified before publishing of a unique identifier. However, this needs to be accomplished already nowadays.
Ad 3) It is in the interest of the author himself to keep her/his information up-to-date. Technically this appears to be the only feasible solution anyway.
Ad 4) I agree with Jason Kelly that unique identifiers need to be based on an open standard. Its use will only develop fully if it will be accepted by as many databases as possible.

Thanx for pushing this important discussion.

Lukas Jeker