Recently on Nameberry there was a discussion on the U.K. vs. U.S. nickname/full name trends (which I also mentioned in a short blog post last November). However, I noticed a pattern with regards to nicknames and the S&H saeculum; in April 2009 Laura Wattenberg posted on how (particularly with boy's names) during the last Depression turned from more formal to more nicknamey/boyish. Looking at some of the U.S. stats between now and then led me to notice the pattern described in the next paragraph (these are just my projections from a U.S. perspective, and is primarily applicable for that location).
The desire for formal names peaks during Third Turnings (Unravelings), when people want to be the best they can individually (notice how there's also an obsession with "early resume building" for children during these times, following with that discussion on the Nameberry thread linked to above). We recently left such an era, which we had been in since the mid-1980s or so. During Foruth Turnings (Crises), such as the current time and (before) the Depression/World War II the obsession with formality in names drops. The desire for shorter names peaks during First Turnings (Highs) (e.g. the 1950s, and the era we'll probably be in within 15-20 years or so) and turns back to longer ones during Second Turnings (Awakenings) (e.g. the 1960s-1970s era, and we'll probably be in one circa 2050).
What does this mean? Over the next few years to decade or so, we'll likely see the obsession over names being "formal enough" fall and the number of birth certificates with nicknames on them will increase some.