Example of address obfuscation:

1. I give a virtual address to my contact (for instance, on a web form):
Contact's address: [email protected]
Virtual address: [email protected]
Hidden address: [email protected]

2. Contact sends message via virtual address:
[email protected]   >>   [email protected]   >>   [email protected]

Spamex also creates a surrogate address -- [email protected] -- for [email protected]

3. I reply using the surrogate address:
[email protected]   <<   m[email protected]   <<   [email protected]   <<   [email protected]

Result:
The contact -- [email protected] -- never sees [email protected]. My address always appears to be [email protected].

Links to Spamex examples:

http://www.spamex.com/tool/aliasinfo.cfm?v=3632914 -- [email protected] (heavily spammed example -- history, contacts -- OFF)

http://www.spamex.com/tool/showhistory.cfm?v=9267498 -- [email protected]

http://www.spamex.com/tool/aliasinfo.cfm?v=1336261 -- [email protected] (spammed -- history, contacts -- whitelist)

Useful links:

http://email.about.com/cs/dispaddrrevs/tp/disposable.htm -- top 10 disposable address services [About.com]

http://us.f308.mail.yahoo.com/ym/dea?YY=78791&y5beta=yes&y5beta=yes -- my Yahoo! Address Guard

http://billing.mail.yahoo.com/bm/Upgrades -- Yahoo! upgrades

http://antispam.yahoo.com/tools?tool=3 -- Yahoo! disposable addresses

Notes:

Adjective: Virtual -- Existing in essence or effect though not in actual fact.

[email protected] is forwarded to my Yahoo! account.