Which leaves us with the question - if "waves" do exist, as they seem to, why do they exist?
Jacques and Janine Vallee addressed this question many years ago, in Challenge to Science: The UFO Enigma:
The development of a wave in any given country generally occurs independent of the happenings recorded elsewhere, news of which reaches the public of the country in question only much later. The newspapers are filled with reports once the interest of public opinion has been triggered by the first important cases, but it does not appear that there is any psychological influence of one country over another in this aspect. Frequently, as a wave develops, it is accompanied by an unusual occurrence, something of a "phenomenon" itself, in the press; the subject appears later and last longer in the newspapers than in reality; at first the press is slow to admit it; then it seeks to prolong its existence. (p. 105)
Looking at this analysis, one can examine the current "wave" (if indeed we are in the midst of one), and point squarely at the O'Hare airport sighting in November of 2006 as the trigger event. As the Vallees noted, at first the press (even the Internet UFO community) was slow to latch on to the case, but then it exploded in the mainstream media in January, where it lingered for a week or two. The ripple effects are still being felt, and there will probably be some sort of renewed interest when the NARCAP report is released.
Add to this the fact that 2007 is the major anniversary year for two very famous cases, Roswell (1947) and The Phoenix Lights (1997), which have already triggered media attention (as has the re-appearance of former Governor Fife Symington III), and you can see that we might be headed not just for a "wave", but a UFO tsunami in 2007. The advent of the Internet has added an extra level of exposure to these events that was not present when the Vallees wrote Challenge to Science.
The Vallees continued their analysis:
Naturally, both on the local and the global scene, a big story disturbs the law of variation; it encourages the witnesses of recent sightings to make their reports public, and, of course, it creates an ideal market for hoaxes of all kinds. (p. 105)
This effect can be expected to more pronounced in the modern era than it was when the Vallees wrote Challenge to Science, simply because the Internet makes the distribution of both witness accounts and hoaxes and frauds much easier (see the Serpo hoax, which achieved meme status quickly, and which some people still think was either real, or some form of disinformation).
The key, as the Vallees were quick to point out, is to distinguish the "signal" from the "noise".
For example, while one might think at first blush that UFOs "waves" are important events, and point to them as a sign of an impending "revelation" (as Whitley Strieber has recently done), they are giving in to the "noise" when they do so.
To use a sports analogy, hockey became much more popular in Los Angeles when Wayne Gretzky was traded there back in the 1990s. Suddenly there was a true superstar in the city, and the media took notice. However, when Gretzky left, things went back to normal - a small fan base, and apathetic media, and a team that was going nowhere fast.
Gretzky was the NHL equivalent in Los Angeles of an O'Hare-type sighting - an event that triggers a paroxysm of interest that builds upon itself, but which cannot possibly sustain itself indefinitely. When memory of that incident fades, or has played out (or, as in Gretzky's case, moves on to another team), things go back to the status quo.
And that's not necessarily a bad thing, at least as far as the UFO phenomenon in concerned, because the sudden interest of the media can detract from the real research being done, usually behind the scenes by dedicated researchers and investigators most people of whom the vast majority of people are unaware, even within "ufology". They don't get distracted by the "noise" (which is - thanks to the Internet and radio shows like Coast 2 Coast more like tinnitus these days) because they understand that it is the "signal" itself which is really important - and the "signal" is there, year in and year out, regardless of whether a major case spawns a "wave" that captures the attention of the general public and the mainstream media for a short while.
After all, there's still NHL hockey in Los Angeles, years after Gretzky moved on. It might not be great hockey these days (the Kings had a lousy year in 2006-07), but its still there, with a small but loyal group of fans, and some good young players, working away at building a team that may one day make another run for the Stanley Cup.
And they still have the memories of the day when the plucky Kings, through hard work, grit and determination to not give up, came back from a 5 - 0 deficit after two periods in the Stanley Cup playoffs to beat... Wayne Gretzky and the mighty Edmonton Oilers!
So too the serious study of the UFO phenomenon.