One point that should not go unmentioned is that what former President Clinton is described as doing in that Times article is little different from what the first President Bush has done in his post-presidency. And his son is the president. So if it would be a problem with Bill, and I think it would be, it unquestionably is already a problem with the current president's dad. And no one has seemed to much bother about it.
Late Update: I dashed this post off quickly. But after receiving a number of emails to this effect, I have to agree that the relationship between a father and son is simply not comparable to that between spouses. So while it's ridiculous that Bush Sr.'s buckraking hasn't drawn more attention, if Bill Clinton were to do this out of the White House the two would simply not be on the same par. Not even close.