The wikileaks cables exist in grey zone; it's they were never released by the US Government, but they are public. Generally speaking if you are not and do not plan on being an employee with a mandated security clearance, you have nothing to worry about. If however, you do have or want to acquire clearance you should not look at Wikileaks since you will be violating the terms under which clearance is granted.
Also, elements of the intelligence community have made statements that suggest that applicants to some government positions could be refused if they tweet or say anything about Wikileaks. [1]
"The collection published today has not been leaked. Assange said WikiLeaks had been working for the past year to analyse and assess a vast amount of data held at the U.S. national archives before releasing it in a searchable form."
If the materials were properly declassified and held for public browsing by the NARA then what Wikileaks is doing is fine. It would be the same as Google wrapping a much nicer search interface across an old dataset.
If the materials were still classified-but-leaked then I won't go near it until it is declassified. But I can't tell from this side of the window what's going on.
