Do the cancer cells escape because the immune system is weak and allows them to do so, or do they escape because the cancer cells change so that they are invisible to the immune system and thus the escape occurs not because the immunity is weak but because the cancer cells are clever and stealthy?
We can have the strongest immune system in the world and if it's the stealth of the cancer rather than the weakness of immunity, we may avoid the common cold but still succumb to cancer.
This paragraph from the Nature article (available online last week) would imply that it's more a change of the cancer cells and less a change in immune function:
"Schreiber, Smyth and Old speculate that from the immune system's point-of-view, a cancerous cell may look like a cell infected by an invading microorganism. To overcome the safeguards that prevent the immune system from attacking the body's own tissues, the tumor has to have a high level of immunogenicity, or ability to provoke an immune reaction. Cancer cells can reduce their immunogenicity by changing the materials they present to the immune system to more closely resemble those presented by normal tissue. This enables the third outcome of the immunoediting theory: escape."
A friend on the LEAD'ers list found another article about immunoediting (one of the authors is Mary (Nora) Disis) and it, too, seems to say that it's more about the cancer and less about the immune system. This is from 2006 and they were already using that term "immunoediting". The full text is dense - I'm busy packing to move and have not read it all. Here's one relevant quote gleaned by the friend who did read it, and a link to the whole PDF at the end:
""Research indicates that tumors evade the immune system following immunosurveillance by either directly inducing tolerance or by altering their phenotype to suppress or evade immunity. This latter mechanism has been termed immunoediting."
http://www.jimmunol.org/cgi/reprint/177/3/1526.pdf
Debbie Laxague