Acid precipitation of proteins or lipids: confused

[hanhan2008]

I noticed that trichloroacetic acid (TCA) is used for precipitating proteins, while phosphotungstic acid is used for precipiting/extracting lipids (seems that proteins and lipids can be separated this way).
So, could anybody explan it in details? Are these two acids really so different and so specific in doing their respective jobs?
IN addition, could anybody comment on DNA precipitation using streptomycin sulfate?
Happy Christmas to everybody!