Querystring dilema

[elleager]

I wondered if anybody could pass judgement on whether the following would effect the quality of a website from an SEO perspective and whether it may jeapordise the websites chances going forward in the eyes of a search engine.

I am currently working on a website that has its own tracking in place to collect data regarding web traffic to the homepage. It does this by using a number of different source id's
to represent different paths to the website.

For example:

http://www.xxxxxxx.com/?Source=1
records that the user came from Google PPC

http://www.xxxxxxx.com/?Source=2
records that the user came from Yahoo PPC

and so on...

Will the addition of the querystring forming part of the URL effect the quality of the website in terms of SEO? Is the use of the Source ID's classed as "bad practice"?

Any advice would be greatly received.

[beu]

Not a bad practice at all but, it may thin out PR. Search engines see these two URLs as two different pages.

[elleager]

Thank you for your response.

Because each ID id classed as a different page, would the site then not be penalised for mass duplication of content? There are almost 100 Source ID's and as you said, if each one counts as its own individual page, would this not be greatly detrimental to the website?