("Regular" PGA Tour events are those tournaments that are not majors, not World Golf Championships events, and not short-field events. Majors have their own cut policies - see links below - and WGC tournaments do not have cuts. The PGA Tour's winners-only season-opener also does not have a cut.)
The PGA Tour cut rule last changed in 2008, when the tour introduced what came to be known as "Rule 78," a rule that proved quite controversial. So controversial that little more than a month after Rule 78 was first applied, the PGA Tour Policy Board voted to changed it. The result was the PGA Tour cut that exists today, as described in the first paragraph above.
About.com Golf wrote about Rule 78 and its rescinding back in 2008. The first post linked here describes that rule, and the second post linked here described the rescinding of the rule:
As noted, major championship have their own cut rule (as do the other professional tours). For those rules, see:
