Google attempting to index the form to access dynamically generated pages. Google has announced about it on last Friday.
Google will choose select menus, check boxes, and radio buttons on the form values of the HTML forms. After access to content pass the form, Google may or may not index that content. Google only retrieve GET forms and avoid forms that require any kind of user information.
This change also does not affect the crawling, ranking, or selection of other web pages in any significant way. It also doesn’t affect of your page rank. According to Matt Cutts, Googlebot is only looking at high quality sites right now. Read the full explanations at Matt Cutt’s blog.
I will have to wait and see how this turns out but for those who want to prevent indexing from Google their dynamic pages for whatever reasons use noindex and nofollow for web pages. You can block Googlebot from crawling your forms by excluding them in your robots.txt file.
Now we have to be cautious a bit more and in my opinion if we have to get indexed only home page we should not use any from on that page ;form inside site does not matter because our home page is serach engine optimized and not other ones.