  The nuclide $^{17}$Ne is studied theoretically in a three-body
$^{15}$O+$p$+$p$ model. We demonstrate that the experimental condition for
existence of a proton halo in $^{17}$Ne can be reasonably quantified in terms
of $s/d$ configuration mixing. We discuss experimental evidences for a proton
halo in $^{17}$Ne. We define which kind of experimental data could elucidate
this issue.
