pronunciaton of OFTEN

Merriam-Webster lists both pronunciations. If it were particularly frowned upon, they'd have some other notation indicating as such. M-W doesn't usually make such pronouncements themselves, though. Their position is just to report the facts that such usage/pronunciation exists.

I particularly like their last paragraph on pronunciation on their web page:

http://www.merriam-webster.com/help/faq/pronounce.htm

where they take exception to the notion of "correct" pronunciation.

You may freely use either pronunciation, /ɔfən/ or /ɔftən/. Both pronunciations are listed in most dictionaries. I tend to use /ɔfən/ because I am an old fart (see mouses) . But I often hear /ɔftən/, usually from those younger than me. But, then, who isn't?
With soften /sɔfən/, however, there is no option to pronounce the t -- yet.

It's often illuminating to use inductive tests when assessing the acceptability of pronunciation variants. There are other examples of speakers who enunciate inert consonants. For the word "salmon", do you find /sæl-mən/ to be equally as acceptable as /sæ-mən/? It's probably not as pervasive as /ɔftən/, but it's common enough in areas remote from salmon habitat. At what level of incidence does a "mispronunciation" become an "alternative pronunciation?" How about /swɔrd/ for "sword," /sʌb-təl/ for "subtle" or /æz-ðmʌ/ for "asthma?" There are almost certainly different standards of acceptability in the U.S. and the U.K for some of these. This again will ultimately come down to descriptivist vs. prescriptivist views, but I think at some point we have to admit that the enunciation of inert consonants is generally defective pronunciation, no matter how widely practiced.

Puts me in mind of the Pirates of Penzance:

Major-General: I ask you, have you ever known what it is to be an orphan?
Pirate King: Often!
M-J: Yes, orphan. Have you ever known what it is to be one?
PK: I say, often.