String theory predicts that there is a huge multidimensional parameter space. Most points in there describe Universes that are extremely hostile and life is not possible. The Universe will quickly collapse, expand to fast so that no structure is left, or find many other ways in why no life can ever be created.
But in this high dimensional parameter space, there exists a small sheltered island where life is possible. Close to the centre the Universe is perfect for life and resources are abundant. Closer to the edges life is barely possible. It is a struggle for survival, but it is possible nevertheless.
Remembering the ration of volume to surface of spheres in higher dimensions, it becomes quickly evident, that in a high dimensional object, almost every point is close to the surface. It becomes only worse considering that the actual shape is not a sphere but has a complex geometry. If we randomly select a Universe from all the possible ones, given that life must be possible, in more that 99.9% of the cases we will find a Universe where life is only barely possible. If we then believe that our Universe is just one of all possible ones and the only bias we apply is the entropic one, we expect to find a Universe where life is extremely tough.
[illustration from http://www.memo.tv/string-theory/]
In fact the argument does not only apply to string theory plus multiverse, but most complex theories that have high-dimensional parameter spaces. So we may conclude from a bayesian perspective, that life should suck as the parameter space where it is possible in abundance is infinitesimally suppressed.
