How do you verify the authenticity of anything? This is a common problem
in the Real World, and is hardly limited to LoA's.
How do you prove that what was on Pages 1 to (N-1) of an N page contract
contained the words you think they said? I knew a guy, back in the early
days, who habitually changed the SLA's in his contracts so that he could
cancel a contract for virtually no reason at all ... the folly of mailing
around contracts as .doc files in e-mail. But even failing that, it's
pretty trivial to reprint a document, so where do you stop, do you use
special paper, special ink, watermarking of documents, initial each page,
all of the above, etc?
Look at what people are willing to go through with paper checks to
increase the chances of authenticity. Google Abagnale.
The real world already has ways of dealing with fraud and forgery, and
while the paper is certainly CYA for the provider, it does provide an
actual trail back that can probably be followed to some party. To refer
to it as an "illusion" is only vaguely true. It is an illusion in that
it will not prevent all cases of hijacking. Of course. However, it is
another step that makes it significantly more difficult for someone to
just start announcing random bits of IP space.
It's just like physical security, in many ways. Given a sufficiently
determined attacker, any door can be broken. Wood door? May require
only my boot. Steel door? Prybar. Bank vault? Explosives. Etc.
The thing is, as you increase the level of protection, the ease of
countermeasures typically decreases (I wear my boots almost 100% of
the time, I may have a prybar nearby, but I am unlikely to be carrying
explosives at any time.)
So let's not trivialize improvements such as LoA's which reduce the ease
of hijackings, eh.