Visitor Form Creating Hundreds of New Page-Detrimental to Page Function & SEO??

Our URL is www.nyc-officespace-leader and it contains approximately 70 pages. It is designed using Drupal 6.12. New pages are being added to our site by a visitor form. Whenever the form is completed a new page (with an independent URL) is created. These pages are not yet indexed by Google. Drupal is not adding them to the site map, but they are visible with programs such as Xenu Link Sleuth.

We are concerned that these hundreds of URL’s may greatly impair our SEO ranking as well as interfere with the function of our site.

The form in question is generated in the following manner:

-Visitors view “Featured Listings” pages such as http://www.nyc-officespace-leader.com/featured-listing-six
-They click on the email address (alan@metro-manhattan.com) on the bottom of the description.
-A form such as http://www.nyc-officespace-leader.com/contact-us?subject=Featured+Listin... appears.
-The form remains as a page that can be indexed.

Can the pages created by the forms be detrimental to our search engine ranking? Can they interfere with the proper functioning of our site?

Is it advisable to redesign the site so these independent pages are not created? What would be involved in such a redesign?