The information gathered by an N-element synthesis array
varies as 
for large N, so linking four new antennas to
the VLBA would
double the information content of VLBA observations by doubling the
number of correlations, and adding as many as eight new antennas
would more than triple the information collected.
This increased information content would
translate into improved image quality via
World-array experiments have shown that the apparent
simplicity of many VLBI images reflects a lack of information
gathered about the sources more than any intrinsic simplicity of
Nature on these scales. We expect many extragalactic sources to
have complex structures on scales from 1 to 100 milli-arcseconds.
Physical interpretation of these structures will require ``movies'' with
high dynamic range and wide fields of view over a large range in
frequency. For studies of rapidly-evolving galactic relativistic-jet
sources, we need the ability to construct such ``movies"
from snapshots of 
1 hour duration.