You need to login into gmail account before you see up and down arrows. Are you suggesting that someone will leave her gmail account open all the time on a single shared computer? I don't think so. Google is pretty good at detecting this kind of abuses.
What if you get millions of searches everymonth? Not possible and not worth my time, if I'm your competitor; I will focus on building quality content instead of wasting my time with up and down arrows.
The only defense against this kind of stuff is:
1) Build a strong brand image
2) Build a strong userbases, especially fans. More fans == more traffic from their blogs and social media.