I have been hearing a lot of talk that having a Pop-Under on your site could cause Google to penalize and even "white bar" your site.

I have also noticed many big sites use Pop-Unders and maintain their page rank and placement. Is there a right and wrong way to impliment the Pop-Under code.

If anyone could please give me any feedback that would be great, or even examples of penalties if they have occured.

I've never heard that but you will certainly be penalized by your users. I know I would stop going there.

I don't think Google would penalize, I've never heard of that happening.

As far as users, it wouldn't bother me any, I use Opera which blocks popups.

I use Opera which blocks popups.

Firefox and Nortan Internet security block them for me.

You will only be penalized by your users. I've never seen or heard about google penalizing pop ups.

There was a thing I heard of a long time back, before popups became common, where the search engine would mistake the popup for a redirect and index the popped up site instead of your real site. Though I haven't heard of this happening for years.

I think this might just be a rumor created to stop people using them.

Type(s) of problem (check all that apply):
Hidden text or links
Misleading or repeated words
Page does not match Google's description
Cloaked page
Deceptive redirects
Doorway pages
Duplicate site or pages
Other (specify)

That's the definate stuff that Google bans for - though it does list 'other'.