The mechanism of p53 proteasomal degradation through polyubiquitination is well characterized. The basic assumption behind this mechanism is that p53 is inherently stable unless sensitized to degradation by polyubiquitination. However, a number of studies provide evidence for p53 to be naturally unstable. Consistent with this attribute is the fact that both p53 N- and C-termini are intrinsically unstructured. Recent findings provide evidence for p53 to be degraded by the 20S proteasome by default unless it escapes this process. A number of mechanisms were demonstrated and proposed to play a role in rescuing p53 from default degradation. These mechanisms, their biological implications, and relevance to cancer are reviewed in this article.