That's a useful corrective, but I don't feel so negative. Our field is not that huge. It only feels that way because of the increasing specialisation. And this is all a good reason for post graduate students to become minor experts in as many topics as possible. After all, one has to teach across a range of subjects; some intensive course work on a given topic can persuade one of how to approach a consensus well.
In the nature of things we're stuck with increasing specialization for the foreseeable future and the only way to work around it is to keep an eye on what other people are doing and start from the consensus position, if there is one, when moving outside one's immediate research specialty either for teaching or research. We've even reached the point of specializations within specializations. It used to be that Qumran studies was a subfield of biblical studies. Now it is not only an independent field, it's one that itself contains various subfields. I can't form an expert opinion on every question in Qumran studies even though it's one of my areas of specialization. I don't have expertise at all on the archaeology and even for the texts I don't have time to do the necessary intensive study of each text to have off-the-cuff fully-informed opinions about all the problems associated with it. I just try to look at some of the secondary literature and to focus on specific problems when my research requires it. When I teach -- even honours seminars on Qumran, let alone introductory Bible classes -- I rely very frequently on consensus positions rather than my own intensive research. I expect Mark does the same. If not, my hat is off to him.
UPDATE: In an update to the same post, Mark replies, "Actually, I research everything I teach on in infinite detail and that's why I never sleep." Oh, okay. I thought he never slept because of all the blogging.
Seriously, read his whole update, which has some good advice on how to stay on top of your field. Let me add that you should be sure not to miss the beer (yes, and whiskey) drinking after the conference seminars. It may impair your judgment, but it's a good opportunity to hear experts summarize what they're thinking about current issues in the field.
Just noticed I had forgotten to link to Mark's post above. Now remedied.