Please please please never disable zooming.
Ok, you might have thought you got your website design right, you might have thought that you got every font size right, and every photo was clear enough that your users never needed to zoom in on anything.
So your users would come to your site, the mobile version would kick in, and they would merrily scroll up and down, never even thinking of a need to zoom.
But just to make sure, you went and did it didn't you, you went ahead and blocked zooming, just to be really sure that they knew what your intent for the website was. Your zoom blocking code never gets used anyway because your website is so perfect, but it's there and that makes you feel better. Maybe it forces your testers to check the site in a certain way. Anyway, theres some reason that you've convinced yourself is valid.
Then some poor person tries to navigate to your website on their iphone in the car. They are just trying to find a postcode. They want to copy and paste it into their satnav app. The kids are screaming. The wife is getting impatient, and your user is desparately trying to zoom in. Some crazy formating or other weirdness makes him keep selecting the whole block of text. He just wants the postcode. He tries to zoom, again and again. He just wants to zoom in enough so that he can get the whole postcode HUGE on the screen, to make it as easy as possible to drag a box round the text he wants. No, that wasn't in your usecase. He tries rotating his phone, no better. The wife starts crying now. Things are getting desperate. He finds a damn pen in the door pocket, buried in tissues and sweet wrappers and writes the postcode on his hand. It's a scratchy pen and it draws blood before any ink comes out. Then he angrily quits your 'web app', loads his satnav and types it back in, nervously hoping he doesn't confuse an L for a 1 and end up on the wrong side of the country.
He now hates your website and your organisation, he's closer to divorce, he's late for the wedding, his patience is drained, he hates his phone, and his wife thinks technology is a waste of time.
Just because you had to scratch that itch.
By all means, optimise your site for mobile if you want. Spend hours and convince yourself that it's lovely. But let your users decide whether they zoom or not. They know their needs better than your ability to predict the entire world's needs.