Advice from Snopes.com:

1) Any time you see an E-Mail that says forward this
on to ’10’ of your friends, sign this petition, or
you’ll get bad luck, good luck, or whatever, it almost
always has an E-Mail tracker program attached that tracks
the cookies and E-Mails of those folks you forward to. The
host sender is getting a copy each time it gets forwarded
and then is able to get lists of ‘active’ E-Mails to
use in SPAM E-Mail s, or sell to other spammers.

2) Almost all E-Mails that ask you to add your name
and forward on to others are similar to that mass letter
years ago that asked people to send business cards to the
little kid in Florida who wanted to break the Guinness Book
of Records for the most cards. All it was, and all any of
this type of E-Mail is, is a way to get names and
‘cookie ‘ tracking information for telemarketers and
spammers – – to validate active E-Mail accounts for their
own profitable purposes.

You can do your friends and family members a GREAT
favor (PLEASE) by sending this information to them; you will
be providing a service to your friends, and will be rewarded
by not getting thousands of spam E-Mails in the future!

If you have been sending out (FORWARDING) the above
kinds of E-Mail, now you know why you get so much SPAM!

Do yourself a favor and STOP adding your name(s) to
those types of listings regardless how inviting they might
sound! You may think you are supporting a GREAT cause, but
you are NOT in the long run. Instead, you will be getting
tons of junk mail later! Plus, we are helping the spammers
get rich!

Let’s don’t make it easy for them!

Also: E-Mail petitions are NOT acceptable to Congress
or any other organization. To be acceptable, petitions must
have a signed signature and full address of the person
signing the petition.

Read the full story here:
http://www.snopes.com/inboxer/petition/internet.asp