Anonymous vs false IDs

There is a lot of effort being put into creating tools to mask identities.
I'm curious why people don't go a different route - creating a false
electronic identity? If you have control over your own system, it is easy
enough to create an account. Lacking that, there are a lot of companies
out there offering low cost accounts on Unix systems with full Internet
access. Why not get an account in a different name rather than using
anonymous remailers?

  I can see some reasons for going both routes, I'm just curious as to
other people's reasons.

-David