Yes. I know cause I hit it with my mellon tonite.
Traded mountain bikes with my bro for a while. Since its too wet to huck, I gave him one of my fulls supension bikes and thought I'd try out his 29er hard tail: A Kona Unit (he put full gearing on it so its no longer a single speed). Nite ride, solo about an hour and a half into it, almost to the spot were I need to change batteries for my lights. Dual beams on the bars and single on the helmet. Trails are tight and rutty and very wet (love those hydraulic disc brakes, not like rim brakse of the old days!). Standing up, off the seat pedaling, head pointed down to see the ruts and stumps and rocks of the trail, no periphial vision due to the nite lites and POW, right into a fallen tree that was crossing the trail at about 5 feet off the ground. Scared the living heck outta me, never saw it coming. Just rode that trail a couple days ago and it wasn't there. Ferricken OUCH!
Broke my helmet, but my lite survived thanks to the quick release to the back of the helmet. I just layed there in the mud for about ten minutes, dazed, still clipped into to my EggBeater pedals. Looking up into the forest all i remember thinking is "Wow, its so nice out here at night".
How much longer till daylight savings time?
I'm glad it wasn't any worse. It sure makes you feel stupid, doesn't it? The day before yesterday I was standing on a piece of landscaping equipment. I turned to jump down and misstepped. Ended up on my butt. My first thought was "You dumb a&&, that wasn't a very good idea". 
