  Collective, explosive flow in central heavy ion collisions manifests itself
in the mass dependence of $p_T$ distributions and femtoscopic length scales,
measured in the soft sector ($p_T\lesssim 1$ GeV/c). Measured $p_T$
distributions from proton-proton collisions differ significantly from those
from heavy ion collisions. This has been taken as evidence that p+p collisions
generate little collective flow, a conclusion in line with naive expectations.
We point out possible hazards of ignoring phase-space restrictions due to
conservation laws when comparing high- and low-multiplicity final states.
Already in two-particle correlation functions, we see clear signals of such
phase-space restrictions in low-multiplicity collisions at RHIC. We discuss how
these same effects, then, {\it must} appear in the single particle spectra. We
argue that the effects of energy and momentum conservation actually dominate
the observed systematics, and that $p+p$ collisions may be much more similar to
heavy ion collisions than generally thought.
