  We examine the effects of disorder on striped phases in high-temperature
superconductors and related materials. In the presence of quenched disorder,
pinning by the atomic lattice - which might give rise to commensuration effects
- is irrelevant for the stripe array on large length scales. As a consequence,
the stripes have divergent displacement fluctuations and topological defects
are present at all temperatures. Therefore the positional order of the stripe
array is short ranged, with a finite correlation length even at zero
temperature. Thus lock-in phenomena can exist only as crossovers but not as
transitions. In addition, this implies the glassy nature of stripes observed in
recent experiments.
