I haven't really used Ettercap (or any other data sniffer) in years (we're talking 2002 or so), one thing to keep in mind is that you're not going to have much success in sniffing secure (ssl) internet connections; in fact, most services that require login now preform the login through ssl to ensure sniffers cannot capture login data.

You can test by going to www.hotmail.com and noting that it redirects you to an SSL page to input login data; the result, you'll never be able to sniff logins for hotmail, the host is an SSL system which is using a 128bit rc4 encrypted connection.
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