Everybody must made made plenty of these. Case in point:
When I was a kid I saw a gumball machine with a little sign on it, a picture of a kid with braces on his legs, sitting in a wheelchair. The text made a point of the word FORD “branded” on the gumballs and said the proceeds from gumball sales went to treating crippled children. 
I concluded from the “brand” and the picture: Does this mean that if you chew this bubble gum you will wind up like the wheelchair-bound kid in the picture?
It was years before I realized my mistake. :o
Post here some embarrassing conclusion you made, the funnier the better. :o 
Well, I’m currently having an IM conversation with a friend of mine from home, and I thought he told me he was gay. When he said, “I’m coming out,” I assumed he meant “…of the closet” not “…to visit the Boston area.” I really need to pay more attention to context…
There’s a sign at a lot of truckscale weigh stations on the highway-
No Pickups
I figured it meant you can’t pick up hitchhikers, but it means pickup trucks don’t have to be weighed.
Sounds inocuous enough. It’s the thing you have football players sniff to jolt them back to reality after they’ve had the wind knocked out of them.
So far so good.
In French, my mother tongue, salts is “sels”; however, “selles” (same pronunciation) means “faeces”.
You see where this is leading…
For years (I was quite young at the time), I just could not understand why they hadn’t found something less … drastic. Although I could very easily see why the players would spring back to life as soon as they had had a whiff of it.
WARNING: The following post contains moral values left over from the Victorian Era. I can’t help it. Read at your own risk.
The suddenly pregnant teenager belonging to our church sat in front with her parents and brother for the last two months of her pregnancy. For the last month of it, the father of the baby appeared, and sat there with them. There was no announcement of a wedding in the bulletin. The rest of us came to the obvious conclusion, and while we didn’t exactly ostracize the two young folks, still, in our communal embarrassment, we didn’t exactly rush up to her and ask her about her pregnancy. And we certainly didn’t broach the subject with her mother.
However, when the baby was born, we noticed that the baby’s name was listed in the birth announcement in the bulletin as being the same as the father’s. We cornered the friend of a friend and asked her, “DID they get married?”
“Oh, yes,” she said cheerfully.
Well, we all felt just terrible. We should have said something, after all. But then she added, “…at the hospital, right after the baby was born”, so we didn’t feel quite so tacky after all.
we now return you to your regularly scheduled 21st century–spare me the lecture, please, I hear it all the time from my daughter…
When I was little I knew the world was round and turning - but I thought we were inside it.
dodgy
A couple days ago (last Wednesday, to be precise) a friend of mine got a new cell phone. I heard him call his girlfriend, and for some reason the first conclusion I reached was that he must be calling her to get her phone number to enter into his new phone. It was only mere seconds before I realized the huge flaw in this logic.
One of those “As the last word left my mouth I knew how stupid I was” ones.
There is a recycling programme for 'phone books in Australia. The shredded books are used for insulation and the like. The advertisments for the programme featured a cute animation of a monster, a 'phone-book muncher, which chomped delightedly - ooh <slobber> 'phone books! - into the books as the kiddies deposited them. Of course the places for deposit were just a skip with a plastic monster head on the top.
At a dinner party I remarked that it must be very expensive to install a shredder in each bin.
I’ve made many of my own, but the most humorous one I can remember came from my son who was about 4 at the time.
We were at the bank drive through window, patiently waiting our turn, when my son said “Oh, so that’s how it works”. I said “How what works”? He said “The money machine.” I looked over just in time to see a Brinks guard walking into the free standing ATM in the parking lot. He was there to balance and replentish the machine, but it took alot of explaining to convince my son that the man didn’t live in the machine and pass out money.
I was once watching a jeweler work with loose diamonds. He was using needle nose pliers and tweezers to move them around and such. I kept thinking he is going to scrath the hell out of them and them they will be worthless. About 1/2 hour later it finally dawned on me.
This wasn’t I who made a wrong conclusion, but a co-worker, about me that I thought was humorous.
When I first moved out to San Francisco, I was working as a computer operator. I work with this little old Vietnamese women who was a little doll. Anyway, we had a lot of time to shoot the breeze. In our conversations, I had told her that I was married, and I lived in the Castro. For those who don’t know, the Castro is stereotyped as a gay neighborhood (well, there are a lot of gay bars and leather shops, but I digress).
It was weeks later when I brought my wedding pictures in to show my co-corker. She saw that I was married to a woman and not a man, looked at me and said, “You’re gay! How come you married a woman?”
Me: “I never said I was gay.”
Her: “But you live in the Castro. You’re gay.”
I guess that little streotype was ingrained in her pretty good. I had to explain to here that the Castro was a pretty diverse little area. She honestly thought that everyone who lived in that area was gay. Like it was gated gay community or something.
No Chain Services, read the sign at the exit along I-80 in the California mountains.
Gee, I thought, shaking my head as I drove by, what a state, advertising chain-free exits, where you can be sure of finding locally owned and operated gas stations, restaurants, and hotels instead of the usual mishmash of Exxons, McDonaldses, and Motel Sixes.
In my sort-of defense, it was the height of summer. Still…