Citi analyst Mark Mahaney trimmed Google's (GOOG) Q1 and 2008 estimates: Q1 down to $4.50 per share from $4.65, and for the year down to $19.08 from $20. He also cut the earnings estimates of 2009 and 2010.

What to blame? What else? Lackluster paid-click growth, of course. Citing comScore and ChannelAdvisor, he says that Q1's click growth will be flat with Q4 and up 16% y/y. That's down from 4% growth sequentially and 20% y/y.

But Mark's not completely sold, it turns out. Citi's own research, he says, doesn't reflect this 'dramatic growth deceleration.' So he says he lowered estimates to 'cautiously err.' We'd rather Mark just go ahead and tell us what he really thinks, instead of hedging, but fine.

Either way, we expect to see more analysts coming to the same conclusions (and some contrarians refuting them).