I see your point, but it's not like there is some sort of +1 on-off switch. Google has some pretty sophisticated and effective means of detecting linking manipu

I see your point, but it's not like there is some sort of +1 on-off switch. Google has some pretty sophisticated and effective means of detecting linking manipulation; I'm sure the same care and set of safeguards would be put in place if +1 was to be used as a ranking factor. Just a casual mention by Matt Cutts that +1 data is used as a part of the algorithm (no matter how small its actual impact) would likely be enough to drive huge adoption.