  An important ``observable'' of planar N=4 SYM theory is the scaling function
f(lambda) that appears in the anomalous dimension of large spin twist 2
operators and also in the cusp anomaly of light-like Wilson loops. The
non-trivial relation between the anomalous dimension and the Wilson
interpretations of f(lambda) is well-understood on the perturbative gauge
theory side of the AdS/CFT duality. In the first part of this paper we present
the dual string-theory counterpart of this relation, to all orders in
lambda^(-1/2) expansion. As a check, we explicitly compute the leading 1-loop
string sigma model correction to the cusp Wilson loop, reproducing the same
subleading coefficient in f(lambda) as found earlier in the spinning closed
string case. The same function f(lambda) appears also in the resummed form of
the 4-gluon amplitude as discussed at weak coupling by Bern, Dixon and Smirnov
and recently found at the leading order at strong coupling by Alday and
Maldacena (AM). Here we attempt to extend this approach to subleading order in
lambda^(-1/2) by computing the IR singular part of 1-loop string correction to
the corresponding T-dual Wilson loop. We discuss explicitly the 1-cusp case and
comment on apparent problems with the dimensional regularization proposal of AM
when directly applied order by order in strong coupling (inverse string
tension) expansion.
