IMO, as far as you deal with Infopath forms, it cannot be done.At least, through Infopath
The definition of a form (in Sharpoint and I think it shouldn't be much different in Infopath) is restricted to an item, the term for more than one item is called view.
IMO, it cannot be done even for non-Infopath (Sharepointy) forms.
It can be done through one Sharepoint view (for example, by enabling for a view Inline Editing option in Sharepoint Designer 2010), i.e. seeing many items at once, but one can edit/update one item at one time, only.
Please, correct me if I am wrong.