Previously, it was sort of vicious circle for new developers willing to start learning Sitecore. "How can I start working with Sitecore" - one of the most common questions asked at StackOverflow and (mostly non-Sitecore) user groups when enthusiasts wanted to download their developer copy and play with it on his/her local dev. machine.
The problem came from a situation when one could install Sitecore only with having a license file, that could be taken from a client he's already working for. Surely, in order to obtain such a job, one should already have reasonable skills with Sitecore obtained from somewhere. Also, Sitecore installers are also not in the free access and require at SDN credentials to be downloaded, even with SIM tool.
Now the process becomes simpler, as Sitecore is going to provide trial licenses for the developers. Currently, they run a pilot testing of that program, offering just 100 developers trial license, with a waiting list for those who not quick enough to get into first hundred. Please read more at the official source of the trial program here: Announcing the preview of the upcoming Developer Trial Program
Hope this helps to attract more developers in order to fill the lack of professionals on the market.