Lewis Lang writes:

Isn't a unilateral contract also enforcable?

By definition, a contract is never unilateral, as it is an agreement
between two parties. A license, however, can be unilateral: you can
grant a license to your photo to anyone without requiring anything in
exchange, if you wish.

WHy does something have to be in exchange
for something else. A contract is merely an agreement, that's all, whether
something is exchanged is besides the point ...

All contracts must involve some sort of exchange. One person pays, the
other delivers goods or services, etc.

... those that would sign a contract
(ie. a modle release) (perhaps a friend or a relative would be more likely to
sign w/o getting somthing in return than a total stranger or a client) have
given their right and permission for their likeness to be used whether there is
something in exchange (valuable consideration) or not.

Not quite. It's a contract if the model is paid or compensated in some
way. Otherwise it's not. If a model isn't paid, he or she can rescind
the release at will, within limits (if the model withdraws permission
retroactively, it may be possible to recover the costs of doing so from
him or her). Photographers can avoid this by always providing something
in exchange for a release, such as a print or a scan, or money.

It is till a legal
agreement I beleive the same may apply for a witness, that a witness is not
needed, despite what one may have heard otherwise to make a contract "legal."

A witness is not needed in general, although some jurisdictions require
them for certain types of contracts.

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.