Watch out who you work with !

One thing about third party email is that you associate your name to the list owner (if you rent a list) or with the advertiser (if you broke your DB).
In this kind of case you really need to watch out who you work with (and that becomes a real nightmare if you authorize email campaigns on an affiliation program).

While the ill impact of working with bad list owners (identified by users are spammers) and associating your brand to them is quite obvious, I think people under estimate the risk of sending third party email campaigns on their list for known ill advertisers.

The best example is an insurance comparison site in France that had real bad email practices for several years, now, whenever I receive advertising for this company from another list, I often unsubscribe directly from the third party program or from the entire program sometimes (and I'm that close to click on the report spam button).

Not taking into account the marketing pressure feeling you get concerning a brand even though you receive it from diferent sources.