  The astrometric data on the runaway star BD+43 3654 are consistent with the
origin of this O4If star in the center of the Cyg OB2 association, while BD+43
3654 is younger than the association. To reconcile this discrepancy, we suggest
that BD+43 3654 is a blue straggler formed via a close encounter between two
tight massive binaries in the core of Cyg OB2. A possible implication of this
suggestion is that the very massive (and therefore apparently very young) stars
in Cyg OB2 could be blue stragglers as well. We also suggest that the
binary-binary encounter producing BD+43 3654 might be responsible for ejection
of two high-velocity stars (the stripped helium cores of massive stars) -- the
progenitors of the pulsars B2020+28 and B2021+51.
