...at least, in so far as a real measurement of how the teams rank before the season. When a team can just retool each season with recruiting at every level, not just the freshman level, the preseason rankings are not so useful.
They will still have meaning (or, rather, importance) in the sense that people (even the rankers/voters) will give them too much credit, and therefore slide teams up and down from their original rankings rather than rank them fresh once we see how they perform.