An iterative encoding technique assesses trial watermark encoding of an object, and redresses any detected shortcomings in one or more successive re-encodings of the object. Other improvements concern web crawler-based watermark detectors, novel uses of meta-data in watermarks, applications of watermarks in merchandising, embedding of active computer code via watermarks, watermark-based asset management systems, watermark processing of computer system clock signals, and watermarks in labels and tags.