Over the weekend, the number of blogs we monitor at PubSub.com passed over 8 million. As of a moment ago, we were monitoring 8,049,578 blogs, of which we consider 4,591,573 to be "active." (Currrent numbers are always shown on our home page.) I believe that 8 million is the largest number of blogs being monitored by any of the various search engines, directories, etc. that provide coverage of the blogosphere.
The many pundits, journalists, etc. that have recently claimed that there are only 10 million blogs are clearly underestimating. At PubSub, we are very well aware that even though we've managed to find and monitor 8 million blogs during the year that we've been providing our service, there are many more blogs that we haven't located and some that we haven't tried very hard to find... For instance, we don't handle Chinese, Japanese and Korean very well at present and thus haven't made much of an effort to track down the many millions of blogs that use those character sets. It should also be noted that we only monitor blogs that have RSS or Atom feeds and we can't monitor "private" blogs that don't publish their feeds or that require authorization to read their feeds. Even with these limitations (to be addressed in the future) all indications are that the rate at which we discover new blogs is not slowing. Thus, I'm very confident that there must be at least two to three times as many blogs then those we've already discovered. That would put the minimum blog census at 16 million while there are probably more than 24 million blogs. Personally, I would bet on the higher number.