I got 3 on the first pass but knew it was wrong, so I went through it backwards (as Munch suggests) and found all 6. I always use the backwards trick whenever I have to enter a credit-card or phone number.
I got six. I do a lot of proofreading in my job, but I’ve also seen this before.
I got all six but I will admit I went the lazy-geek way about it and used “ctrl-f” without even reading the actual passage. Technology is power.
Hijack - is it true that 5 is the biggest number your brain can process without subconciously splitting it into smaller numbers?
The greatest variation on this OLD gag was on the Penn & Teller Cruel Tricks for Dear Friends book. You had your friend read the text on the back of the book and count the F’s. When they give you the answer, you secretly peel off the vinyl sticker that was covering the phrase which has a similarly worded phrase with a different number of F’s. They’d never get it right and never figure it out.
I got seven. Go back and look at it again, very closely.
Ok, actually I failed. Only counted three.
I counted all 6. I’d seen it before, but I counted all 6 the first time too. The reason is that I knew that whoever came up with the puzzle was trying to trick me, so I needed to pay extra attention when counting the Fs.
I learned this trick as a kid. Now when somebody asks me to count something like this, I’ll generally go through the words backwards without reading the text. That way my phonics section doesn’t kick in.
“Trying is the first step toward failure!” - Homer J. Simpson
I failed. 
This is related to that nifty study about internal letter ordering being less important to reading than having the correct first and last letter. Reading occurs a tiny bit above the word level. My former advisor does tons and tons of research using letter detection tasks, where subjects have to read a passage and circle all the instances of the letter ‘a’ and similar things.
You also see some interesting results in eye tracking studies with regards to what sections get second and third passes, and how long those passes are. Of course with eye tracking studies you are dealing with really fancy equipment to measure millisecond effects that no one can quite agree on the interpretation of. This is how we now know that psychology is a science.
I’ve seen this one before, so of course I knew there were six Fs.
That said, I failed it the first time it wa presented to me, when I only counted three Fs. I first saw this in the seventh grade when my band teacher presented this exercise to us. The purpose was to help make us aware of subtle details when reading music.
I counted 3. And I’ve seen this test likt 5 times before. I BLAME IT ON BRUSSEL SPROUTS!
Yes another who got 3 here.
<shuffling over to dumbass side of room> 
I’ve seen this before, and I still missed three the first time I read it.
I got all six, when I got to the end I noticed an “of” and recounted properly.
I somehow also got 5…not sure which one I missed. Oh well. I missed the Ofs the first time, then read it backwards and caught them…err some of them.
Actaully this number varies from 5-9, and refers to the number of discrete numbers your mind can hold in memory at once. You might be able to hold 293742654 in your mind just fine without converting it into a word or subdividing it, but add one more and the first one pops out of memory. Most people can remember 7 with no problem, and this is why phone numbers are that long.
Oddly enough, I came up with sixty-two.
I got six, but I did look at it twice…I definitely know I scanned over the first two “of’s” the first time.
I found all six, but I have seen these before 
I got 3, when this was first shown to me, years ago.
How would that help? I thought the point of going forward is that when you reed a sentance like this, you’re mind fixes all the mistake automaticly, because it knows what it should say. “Automatically” makes more sense than “automaticly,” so you can miss it easily if you’re not paying attention. But 8409382 doesn’t make any more sense than 8490382, so how does this help you exactly?
I forgot to add that, as all the Ctrl-F’ers above have proven, our inability to pass this kind of test is one thing that sets us apart from artificial intelligence.