capacitors

On "larger" capacitance values in "smaller" packages. Some wisdom has been that
while you _can_ get 10uF in 0603, you're going to pay for it, and it might have
even worse dc bias derating than you thought.

Also...

PeterM: If its for dc -dc, or ac coupling, use bigger package, the bigger packages have
    lower ESR and better DC bias characteristics. However if it is for an
    mcu/fpga/asic/mpu or any high speed digital, use smaller packages for lower esl,
    and the dc bias is going to be low enough it shouldnt effect it much
AA: isn't the DC bias for a bypass cap application whatever the voltage rail is? 
    e.g. 1.8V, 3.3V, whatever? and if you're using a 4V cap isn't that going
    to derate it significantly?
PeterM: Yes dc bias is the voltage of the rail, but the effect of dc bias on the cap
    is dominated by the caps package, not its voltage rating