The bid-ask bounce is the bouncing of trade prices between the bid and ask sides of the market.  It introduces a systematic bias to the data which can cause serious problems in analysis.

What methods can be used to control for the bid/ask bounce when using high-frequency data?  One approach is to use the bid/ask midpoint, but what about with trade data?  Even using n-minutely VWAP prices doesn't guarantee that you won't have spurious mean-reverting behavior.