Having guest posting or not, depending on your approval setup this particular means of going through posts is daunting and detrimental. There is quite a few ways to accumulate approval queue posts:
Guest posting that requires approval.
User posting that requires approvals (for new members or members currently under surveillance)
Forums that require approval before users post in it (the Sales forum on IPS used to use this feature).
Topics that require approval before people can post in it, this is a special moderator feature for volatile subjects.
Posts in Databases, gallery, calendar, new clubs etc.
Each of these items can end up in the approval queue and can add up over time. While I don't have 50+ on average it doesn't change the fact that the queue is a bad admin experience from a UI perspective, time consuming and overall meh.
Sure. Flag a person as a spammer and be done with it but that doesn't resolve the issue overall on extremely popular sites. Additionally, using other methods (going directly to forums, databases etc with pending items, doesn't make for a good experience either. This should be an all in one easy place for us to view what is pending and be able to approve, delete or hide any necessary pending approval content.
I'd dare say it would be nice to have filters like:
All pending items from X user
All pending items from X IP
But I digress. This has been a pending suggestion for almost 2 years so at this point I'm sure its being ignored but it is a much needed change.