The human face is more powerful to our brains than any other thing we see. It's how we read each others intent, feelings, sincerity - well everything. I have seen so many companies create websites and other marketing materials using only words or abstract images. I get the power of both when done perfectly. But most often, you will increase response if you 'humanize' your communication. It just works. It's the way we're wired. Of course trite, insincere pictures of people can take it the 'other way'. Yup, everything requires good execution. Darn.