Genomes and knowledge - a questionable relationship?

The availability of bacterial genome sequences has ushered in an era of post-genomic research - accelerating and often enabling molecular genetic analyses. For bacteriologists focussing on an individual bacterium, comparing genomes has also led to a greater understanding of their favoured organism through contextualization. But how does the value of such contextualization vary with the number of available genomes? It seems that for most genome metrics, comparison against approximately 100 genomes is sufficient, with comparison against further genomes not considerably affecting the contextual knowledge gained. It appears that quality, rather than quantity, might be the most important factor when comparing genomes.