Oh my God! No idea how it exactly happened but I'm not going to tinker around to find out!
Just like everybody else, my Wifi option in "Settings" was grayed out with "NO WIFI" in its place.
I've been having this problem for the last two days, busting my head over the issue. I tried everything on the forums, I called the Apple folks and tried their list of solutions. I rebooted, refreshed, restored, reset - everything. I was awaiting a call back from Apple when the problem was fixed. FIXED.
This is what I was did:
I had recently rebooted my iPhone. As soon as the lock screen opened up, I QUICKLY slid open the lock screen and accidentally clicked on a weblink bookmark on my homepage. The cell network was still "searching" while safari quickly opened up. I started getting a barrage of messages starting with the likes of "no internet connection", etc. Than all of a sudden it made a reference to "wifi" (I didn't read it, I was closing them almost as they popped up as it was a mere accident I got into it). After I got back to my home page, I checked settings and there it was. WIFI was activated again!!!!!!
It seems that by attempting to access some some (or all) connection types while the iPhone is still loading up can activate that shut off Wifi option.
PLEASE let me know if this works so that I can spread it on the other threads.