  We present a multiwavelength analysis of 63 Gamma-Ray Bursts observed with
the world's three largest robotic optical telescopes, the Liverpool and Faulkes
Telescopes (North and South). Optical emission was detected for 24 GRBs with
brightnesses ranging from R = 10 to 22 mag in the first 10 minutes after the
burst. By comparing optical and X-ray light curves from t = 100 to about 10^6
seconds, we introduce four main classes, defined by the presence or absence of
temporal breaks at optical and/or X-ray wavelengths. While 15/24 GRBs can be
modelled with the forward-shock model, explanation of the remaining nine is
very challenging in the standard framework even with the introduction of energy
injection or an ambient density gradient. Early X-ray afterglows, even segments
of light curves described by a power-law, may be due to additional emission
from the central engine. 39 GRBs in our sample were not detected and have deep
upper limits (R < 22 mag) at early time. Of these, only ten were identified by
other facilities, primarily at near infrared wavelengths, resulting in a dark
burst fraction of about 50%. Additional emission in the early time X-ray
afterglow due to late-time central engine activity may also explain some dark
bursts by making the bursts brighter than expected in the X-ray band compared
to the optical band.
