One of the questions being asked in the wake of the stock hits that Google, Yahoo! and FindWhat took last week is: Can search engine marketing growth be sustained? If the attendence at this year's SES show is any kind of anecdotal evidence or answer to the question, that answer is "yes."
By my highly informal survey, there are many so-called "newbies" here. That is, there are many advertisers that have been doing search for less than a year and some that haven't yet really adopted search marketing. The frenzy of this conference, its zoo-like attendence (two floors of exhibits) and the fact that there are lots of folks here that are new to search suggests that interest and growth are sustainable.
On the more "empirical" side, the fairly limited numbers of marketers currently involved in SEM vs. the market potential also indicates we are quite far from a mature market. Having said that, SEM is a "fragile" medium that has lots of complex, moving parts that makes it quite a bit less predictable than traditional media, such as Yellow Pages, newspapers, even TV.