'Of'en' is what I generally hear but, yes, 'often' is creeping in. It's based on the fallacious idea that words have to be pronounced as they are spelled.

"Three months later I was on a Norwegian freighter out of Halifax harbor heading for Liverpool, leaving a tiny untidy apartment and a perfectly nice girlfriend."
Norm Macdonald

Ships are said to be 'out of' a certain port. One might speak of a freighter 'out of Amsterdam', which presumably refers to either their port of registration or of departure.
The 'based' part is redundant.

Will, we'll have to agree to differ. The language that people use, both in speech and writing, is, as I said above, endlessly fascinating.

Will - one can make judgments about English usage so long as one's comments are not ad hominem. I agree that it's bad manners to correct others.
The language of others, though, is not of infinitesimal importance to me. I find it endlessly fascinating.
By the way - 'judgment' or judgement'? The latter is more usual in British English but I have a fondness for the former because it was the spelling used by Dr. Johnson, that stalwart layer down of the law.

Will - interesting question: 'does it really matter?'
If these issues simply don't matter, then English becomes a relativist free-for-all and judgment is impossible.

When I make a dogmatic statement such as "such and such a word does not exist," I suppose I mean, "Well if it does, it flipping well shouldn't." Grumpy old man syndrome.

Point taken, Will.
The plurals that irritate are words such as 'behaviours' used in certain specialized fields jnstead of 'forms of behaviour'. Cant usages tend to seep into the spoken language.

The word 'correspondences' does not exist in English.
One can refer to the 'correspondence' that one had with Joe Blow. That can refer to one or more letters.

I've never heard 'ideal' used for 'idea'. Maybe it's an American thing.
I notice, though, that 'ideal' is often pronounced with two syllables instead of three. That makes me raise an eyebrow like a pretentious douchebag.