  In the past years, variable speed of light (VSL) theories have been of
growing interest but also a subject of controversial discussion. They have been
accused both for tautologies and for violating special relativity, and concerns
have been expressed about the validity of such approaches in general (e.g.
Ellis, astro-ph/0703751). Without trying completeness on the issue, the example
of Einstein's VSL attempts (1911) and Dicke's `electromagnetic' theory (1957)
are urges to give some comments on the above criticism.
