Google spidering other paid placement search results

Are these links seen as duplicates?

[sublime1]

Recently one of our sites got mostly eliminated from Google SERPs. We have gone through the checklists and done everything we can think of to make the site is squeaky clean, but of course only have theories about why our top SERPs which we have had for a year have been killed (sigh!). Here's one theory:

Using the Google query "site:www.example.com" results we see that Google has been spidering links from paid placement/inclusion sources (e.g. inktomi, enhance). These links have tracking parameters in the query string (e.g. http://example.com/mypage.html?source=enhance&kw=widgets). The parameters don't do anything -- the same page comes back with or without them. Will this confuse Google or cause them to think we're perpetrating duplicate content or otherwise be bad?

A second issue is that with Inktomi/Yahoo's paid inclusion we're seeing URLs that Google is spidering but which are still URI-encoded (e.g. http://example.com/mypage.html%3Fsource%3Dinkt). Since the URLs are bogus, our servers are reporting a 404 error. I certainly hope this is not triggering removal of the real page from the index, although that seems a little far-fetched :-)

And of course, why the heck is Google spidering search results pages from other engines?

Thanks in advance.

[edited by: engine at 5:41 pm (utc) on June 14, 2004]
[edit reason] de-linked and examplified [/edit]