Opposed checks and flat footed targets


There is something that has troubled my mind lately. When you attempt special attacks like grapple, disarm, trip, etc., you have to do an opposed STR check usually I think, though with trip you can also use DEX. Is there any effect if the target is flat footed or feinted or the like when you make such an opposed check? It gives me the impression that the defender could be at a disadvantage, as they are defending (opposing) such an attack. Can you infer this from the rule flat footed (and the like), or not?
Nope. Flat footed opponents cannot Dodge or Parry, but since those aren't options against the types of attacks you mention, they work normally.
No, just like Sutek said, opposed rolls (Str, Dex, or opposed attack rolls for Disarm) aren't affected. You get other advantages against flat-footed opponents however...

For one, many of these special attacks provoke an AoO. Flat-footed opponents can't make AoO's (unless they have the Combat Reflexes feat), so you're safe from those. Of course, if you have the appropriate feat (Improved Grapple, Improved Disarm etc.) this advantage 'disappears' since they couldn't have taken the AoO in the first place.

Also, some of the attacks demand that you also succeed on a regular attack roll against your opponent (grapple, trip). This attack roll will be much easier since you'll only have to beat a DV of 10 against a flat-footed opponent.
No, a feinted character gets AoOs as normal.
Being feinted only means you are unable to dodge/parry the next attack made against you by the guy who performed the feint (that attack may therefore be a sneak attack) .
Being unable to dodge/parry is not the same as being flat-footed, and it doesn't incur any special restrictions on AoO.