Steve Kaufmann recorded a video on the importance of memory when learning foreign languages. His take is basically that language learning isn't about memorization. I posted a bit of a rambling comment wanted to revisit my ideas.
I think that memorization is important at the start to give you a basis for actual language use and to allow production sooner. Steve's point of view makes sense if you don't care about production early on or mind listening to audio you don't understand.
The input-only hypothesis says that the required grammar structures and vocabulary will be learned from repeated, real-world exposure. Production should be delayed until the student is "ready" to produce.
Steve is being an armchair quarterback. From the safety of his living room, it's easy to say that 8 months of listening to audio books in Portuguese before trying to speak is a good idea. If he were living in Portugal, his need to communicate would be much stronger and real-life would not afford him the luxury of an input-only timespan.
To get to even A1 of the CEFRL, you need an active core vocabulary of 500 words plus the associate grammar rules so you can put sentences together. Even with flash cards and adding 20 words per day, you're still looking at about a month doing nothing but memorizing.
Like many skills, before reading and writing your target language become natural, they have to be done carefully, step-by-step, by the non-automatic part of your brain. You need to actively remember the gender of nouns, and which conjugation goes with which subject pronoun, the order of words in the sentence, and even the spelling of common words. For me, the need to memorize my core vocabulary and the associated grammar is the Great Wall of China standing between myself and basic fluency.
The need to memorize lots of vocabulary is a requirement for input as well. I'm reading Tintin comics, and it's slow-going. Yes, I can look at the pictures. Yes, I know the story. But there are too many unknowns in the content to be able to extract meaning from them. They are not yet comprehensible input, but with the help of a dictionary and flash cards, the second time they will be.
Unfortunately, it's also easy to memorize the wrong way. Poorly made flash cards can teach you definitions and make you better at solving crossword puzzles, but no better at speaking or writing. AJATT and Antimoon's sentence-based learning methods are the way to go, I think.
Back to Steve's claim about memorizing. He favours instead "repeated exposure until the material has been absorbed", which sounds a lot like memorization to be. And he's also recently been going on about how wonderful his flash cards on his iPod touch are. Again, memorization.
At the other end of the memory scale, there are Laoshu5d05000's "Language Bootcamp", Pimsleur, and Michel Thomas. These courses get people producing output quickly, even if it's in small chunks. They're also an application of the testing effect that basically says if you're try to recall material, you learn it faster.
Finally, for many people, production _is_ the end goal, the "proof" that their work is paying off. (Reading just doesn't cut it, especially with so many European language families being so large and sharing vocabulary. Interlingua, an international auxiliary language, is even based around this fact.) Much could be written about our instant-gratification society (and Karate Kid training montages) but I think that many people would give up before reaching the amount of input required for "natural assimilation" of a language. Sitting down and studying grammar and vocab addresses this problem.
Memorization is a necessary evil in language learning. You can go about it in a number of ways, and flash cards probably make it easier, but in the end there's just a lot of arbitrary sounds and symbols that have to be stuffed into your brain.