[spirochete]

I've attatched a picture of a simple cation with a paticular orientation.  I was told this molecule doesn't have resonance because the P orbitals don't line up.  But couldn't the sigma bond rotate, allowing for overlap?  Am I missing something more complicated here?

[macman104]

I agree.  I'd think the sigma bond could rotate to allow for proper overlap and resonance.  I guess you could say in that *exact* particular conformation resonance may not be possible...

[FeLiXe]

maybe there is some steric hindrance in the planar structure and the relaxed structure would remain slightly bent.

[AWK]

Question concerns this conformation, not that after rotation.
Of course, real allil cation can be stabilized by resonance.