  Kaon photo- and electroproduction in all six isospin channels are
investigated by means of an isobaric model. It is found that existing models
can only partially describe the current experimental data. Moreover, the
extracted coupling constants are mostly inconsistent with the prediction of
SU(3) symmetry or the information from hadronic reactions. In order to further
analyze this problem, we introduce a form factor at the hadronic vertices $KNY$
(with $Y=\Lambda~ \textrm{or}~ \Sigma$) and study its behavior qualitatively.
Our result suggests the need of more accurate experiments, especially in the
charged $\Sigma$ and the neutral $K^0$ channels.
