Meng,
I'm backing Aviastar on this one; it doesn't look good for BQ to cut frequencies to less-than-daily in the face of AA, CO, etc. I've ready study after study about consumer reaction to less-than-daily service in business or VFR markets, and I'd presume that is primarily BQ's mix.
Of course, this is when being big helps. BQ (I imagine) is locked into contracts with Icelandair and Air Atlanta for large-capacity, high-density aircraft. It's hard (and expensive) to get out of those contracts. Alternatively, AA or CO can switch a large aircraft to a smaller with relatively little pain and cost, though the closer in the higher the cost related to crew displacement, etc.
At any rate, I would assume BQ pours over advanced booking data regularly and should have seen this coming. At that point, the decision could have been to get out the larger capacity and figure out how to make it with fewer seats but daily flights.
In the end, frequencies may not - and are not - a sign of who is making more money. But, in the eye of the consumer it is clearly a sign of strength and/or commitment to a market, one which I am sure CO, US and AA will all capitalize on.