I'll (almost) wager REAL and significant money, that it is due to something no server / traffic management sw will track. Sure you'll see some trends... but those will merely be indicators or... "symptoms" of something underneath and behind or essentially "driving" the spike. Unless it is mere coincidence and some of us don't believe there ever really has been such a thing as one of those. (whether or not you get into quantum mechanics OR fate OR providence OR...).
And my wager of what that spike was driven by is, Palm's announcement of their upcoming Treo650. It arrived in my email (server EST time) at approx 11am. So depending on how large Palm's DB is, given they email ALL their past and current customers and more... the Internet itself probably slows notice-ably upon such blasts. Meaning some emails may not arrive for literally hours including spam-and-virus filter processing time w/in many servers, the usual bouncing MOST-inefficiently seemingly around the globe sometimes and all the other usual Internet "traffic patterns" since so few of us are YET on *Real Private* Networks, etc.
Naturally the contributing factors all across the Net may have been that virtually all other sites besides the well-know portal "brands" that came up in Google when I (and obviously others) looked up Smartphone reviews, were QUITE evidently "old" with minimal obvious third party validation as to accuracy, thoroughness and more. (Happily you guys have a bit of an early mover advantage in your segment "below" the known portal brands, who are covering Smart Phone and come up in searches including reviews. Oh and have clearly done a nice job so far leveraging that early mover advantage). Like a few banner ads from industry conferences pertinent to the segment of the given portal, clear lack of reviews of recent product releases ALREADY reviewed by competitor portals, etc. Or dates of posted articles. Took me about 3 minutes flat to weed out the chaf in my google-plus-my-own-pattern-recognition tendencies from having launched so many Internet plays and more over the years. Meaning I found you guys and your posting from early this a.m. regarding this traffic spike that I surfed in upon the wave of, which impressed me in tandem with the other indicators that your site warranted further investigation... and for what this is worth; I haven't signed up to ANY posting facility in years because I simply don't have the time just now - despite fingers flying fast enough on keyboards to generally keep only slightly ahead of my brain.

So second kudos to you guys! IE: Keep up the Good Work! Careful or someone will buy you soon!