I suspect that it will not come as too much of a surprise that voters (in particular, coaches) are biased in terms of which teams they rank high and which teams they rank low. A recent study by Matthew Kotchen and Matthew Potoski ("Conflicts of Interest Distory Public Evaluations: Evidence from the Top 25 Ballots of NCAA Football Coaches") found that football coaches vote in ways that benefit them:
Using individual coach ballots between 2005 and 2010, we find that coaches distort their rankings to reflect their own team's reputation and financial interests. On average, coaches rank teams from their own athletic conference nearly a full position more favorably and boost their own team's ranking more than two full positions. Coaches also rank teams they defeated more favorably, thereby making their own team look better. When it comes to ranking teams contending for one of the high-profile Bowl Championship Series (BCS) games, coaches favor those teams that generate higher financial payoffs for their own team. Reflecting the structure of payoff disbursements, coaches from non-BCS conferences band together, while those from BCS conferences more narrowly favor teams in their own conference.A short write-up about the study can be found at the Freakonomics website ("We Are Shocked — Shocked! — to Learn that College Football Coaches Exhibit a Conflict of Interest When Rating Teams").