I noticed a post on SpringSource's blog site the other day that included some a chart of job postings based on some specified criteria. The blog post was about some recent Red Hat announcement, so one I assumed that the chart was intending to compare Spring against Red Hat.
I'll admit that I haven't done a lot of development using RedHat's technologies (unless you count Hibernate - which is practically everywhere - and RichFaces JSF), but I'm pretty sure that the charts weren't giving a fair comparison. Seam and RichFaces are not all that RedHat (JBoss) is about. I posted a comment, then noticed a day or so later that a blog post from somebody at Red Hat had used the same ad statistics system to show a quite different picture.
When companies advertise for a developer (shameless plug - I'm available at the moment), they're not always after somebody who has specific expertise with the particular application server that they are currently using - because that criterian could eliminate a lot of perfectly good candidates. These servers have to get certified as meeting certain standards before they can claim to be "Java Enterprise Edition" after all.
So, I feel that Rich's chart may be a little more reasonable than Rod's if you look at it in terms of what skills the industry has been seeking from new employees.
I'd rather be hearing about the technologies than the - possibly biased - perceived market trends.
(Spring Security 3.0.0.M1 looks like a great update).