  In this short contribution we consider what types of surveys might be
optimally pursued with path-finding instruments of 1%, 10% and finally 100% of
the projected SKA sensitivity from the perspective of scientific applications
that utilize the red-shifted 21 cm emission line. Achieving interesting HI
galaxy sample sizes with 1% SKA surveys requires very substantial survey
durations, of about 1000 days. Good sampling (log(N)~5) down to below M_HI* can
then be achieved out to z=0.2 over 8000 deg^2 of survey area or even to z=0.5
over 800 deg^2. The same surveys will permit the resolved imaging of order 1000
galaxies in each of several red-shift bins as well as detection of faint
neutral filaments in the vicinity of galaxies with a column density of about
10^18 cm^-2. Once 10% SKA sensitivities are achieved, then ground-breaking
surveys are possible with only 100 day duration. Sample sizes of log(N)~6
extending below M_HI* are possible over 800 deg^2 out to z=0.5 and over 80
deg^2 out to z=1. Such surveys will permit very competitive measurement of
acoustic oscillations in the galaxy power spectrum. One can then envision a
series of 10% SKA surveys probing different depths. With the 100% SKA
sensitivity the capabilities are truly phenomenal. Survey sample sizes in the
range log(N)=7-8 are feasible over the red-shift range of 0.2 to about 5.
Precise tracking of potential time evolution of dark energy (via the baryonic
acoustic oscillation signature) should be possible out to z~3. The local cosmic
web will be imaged down to N_HI=10^16 cm^-2. What exactly will be seen at z > 3
? This will depend crucially on the SKA sensitivity in the critical frequency
window of 350 to 200 MHz.
