In addition to a twitter discussion about lab safety last week, there was a conversation about reviewing manuscripts as a postdoc/junior PI and the value of it, that I thought worth bringing to the blog. The origin was a conversation between CoR and @bam294 about whether manuscript reviewing is a way to increase one's influence. Also, whether doing a number of reviews for a particular journal may lead to an Associate Editor post, which further expands a person's sphere of influence.
The desire to review manuscripts is something I often hear from either postdocs or junior PIs and I admit to seeking them out as a postdoc as well. I think it is a good idea to be involved in the review process from early on, as it helps improve one's own writing. It also sharpens your feel for what reviewers will look for when you submit something. However, I don't see the benefit of carrying a heavy review load pre-tenure. This may sound stupid coming from someone who just accepted the role of AE at journal, but I only did so after ensuring that the review load would not be overwhelming, and after talking to senior people in my dept to see how it would be viewed for tenure.
As much as reviewing can be personally helpful and is an important service for the community, I believe there is certainly a point of diminishing returns. IMHO, I think the cost/benefit of reviewing when it comes to one person's influence is wildly skewed towards cost. This is especially true if compared to attending conferences, getting invited to give talks at other universities and publishing your lab's stuff in journals people read. And if you are reviewing for a journal that keeps reviewer names secret, this is doubly true as only the AE is going to know you were involved.
Don't get me wrong, I think reviewing is a good thing, overall. But I am happy for a month that goes by when I don't get asked to review anything, because I have that much more time to focus on the things that are important for my lab.