When you use the built-in service of tinypic or a a news website or any other website to send emails to friends, I believe the website keeps those email addresses to advertise themselves and even maybe to sell to spammers. After all, they are providing a free service and need to make money somehow. But be aware you are giving out your friends' email adresses.
They may or may not realize what you've done, but they may not like the result.
If you want to avoid this, take the urls and send them to your friends by means of your own email program. It may actually take less time because you have nicknames for most of the friends you email.
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