It is very exciting that the preprint servers like arxiv and biorxiv are rapidly gaining acceptance among the biologists. The process is being aided by blogs highlighting interesting articles in different categories. Our reader Jake wrote -
im a huge fan of both the arXiv and bioRxiv, and have been posting on them for a long time. I too struggle to get my biological collaborators (and even some theoretical ones!) to post preprints for the same reasons you did. I recently took a google poll about this and wrote about it here:
most of the real reasons behind not using the servers are just habits!!!
also, shameless plug, we mathematical oncology folks have a Haldanes Sieve inspired blog too, and we definitely post bioRxiv pre-prints, its called Warburgs Lens and can be found here: