The concept of Planetary Boundaries was front and center at the Rio+20 conference. In the run up to the conference, the Breakthrough Institute released a report highlighting "scientific flaws" with the concept and, as a result, UN negotiators "stripped out all references to planetary boundaries from the Rio+20 text."
This appears to have been an overreaction. A reading of the Breakthrough Report and the response by Johan Rockström (Planetary boundaries: Addressing some key misconceptions) leads to the conclusion that a) some earth scientists interested in getting traction with the policy community appear to have deployed the idea in ways that went beyond what can be justified on the basis of current science and b) the critics appear to be more interested in cutting the head off the concept than in furthering sound debate.
Thus, for example, the critics state categorically that six of the nine planetary boundaries operate at the local or regional scale and don't have global biophysical thresholds. There are two basic problems with the claim. First, it fails to recognize our level of ignorance about many of the topics. New information is constantly appearing. As one specific example, a recent summary of our understanding of biodiversity makes the case for a planetary boundary in that area much stronger. Second, the distinction between planetary level processes and the aggregate of local/regional processes is not as clear cut as the critics would suggest.
A second example relates to the 'environmentalist's paradox'. Here is the summary of the Breakthrough critique:
The planetary boundaries hypothesis rests on the assumption that environmental variables are closely linked to human welfare, and that, consequently, loss of ecosystem services or natural capital implies declining human welfare. This assumption, however, has thus far not stood up well to observed trends with regard to both human welfare and ecological degradation. Over the last few decades, human welfare has improved significantly on a global level, even as a majority of ecosystem services have declined.While this critique does give greater play to the role of time (note the reference to "thus far"), it fundamentally treats the observation as an inconsistency that contradicts the planetary boundaries account rather than as an empirical observation which can be explained in a variety of ways -- only one of which would contradict the planetary boundaries concept.