I haven't read all of Venema's arguments. Does he argue against a bottleneck based primarily on heterozygosity? That strikes me as about the weakest argument one could make.
This is a much broader statement than your previous one. Whether it is true or not depends critically on what timeframe you're talking about. Clearly, a bottleneck of size two that occurred 500 million years ago would not leave a record in genetic variation today, while a bottleneck of the same size 50,000 years ago would.
I tend to be more circumspect in my claims about ancestral population size than Dennis. I haven't done a really systematic study, but my strong impression is that a bottleneck of size two within the last several hundred thousand years is incompatible with patterns of existing genetic variation. If you can fit one in within the last half million years I will be surprised, while a million years wouldn't surprise me. That's based on the the overall allele frequency spectrum. There may be other data that would provide more constraints.