Buyers are influenced by other buyers, especially "important" ones who are technology leaders in their field.  For example, if you sell software to practicing accountants, you want Big 8 firms as key accounts.  For these special lighthouse accounts, consider giving away the software.  You need to be selective as to who you give software to and not give out too much.  One way to avoid the impression that you are bribing someone for their use and testimonial is to give the software as a beta test and solicit their expertise as to how you might improve it.