  This paper is an extended summary of the talk I gave at IAU Symposium "New
Horizons in Time Domain Astronomy" (Oxford, 2011). I first review the history
of transients (which is intimately related to the advent of wide-field
telescopic imaging; I then summarize wide field imaging projects. The
motivations that led to the design of the Palomar Transient Factory (PTF)
followed by a summary of the astronomical returns from PTF. I review the
lessons learnt from PTF. I conclude that, during this decade, optical transient
searches will continue to flourish and may even accelerate as surveys at other
wavelengths -- notably radio, UV and X-ray -- come on line. As a result, I
venture to suggest that specialized searches for transients will continue --
even into the LSST era. I end the article by discussing the importance of
follow-up telescopes for transient object studies -- a topical issue given that
in the US the Portfolio Review is under away.
