Different sectors rise and fall at different rates. The LLL market saw a drastic rise, then a big fall, and now is climbing back up again. LLLL.com's have done something similar however I'm not certain they have seen a rebound as strong as LLL.com's have.
Through the bad economy and all of this though, I don't think there has been much of a change at all in strong generic .com domains. Maybe if somebody were to create a price guide for them they would have told you they went down some in value, but not many sellers seemed to be willing to part with them at discount rates over the last year - believe me I have been looking.
I guess you can compare domain price fluctuations to stocks in the way that Financials, Industrials, Tech, Biotech etc stocks all don't go up and down together. Different types of stocks go up and down at different times for different reasons.