I did an IAmA on reddit that blew up but I was getting slaughtered so I ultimately bowed out. I requested to go on the calendar but was denied since I wasn't famous enough, but encouraged to informally post one. My mistake was that I thought I had to compensate for not being on the calendar by over-marketing myself and really hyping it up. I got destroyed for this, and even when I admitted my error and said "touché" the trolls kept coming at me. I ended up as the top thread on the front page but it wasn't worth it, so I just deleted it. One Redditor actually went through the trouble of buying my book (but obviously not reading it) just to write on Amazon that I was a d-bag.
There's definitely potential to get traffic and eyeballs onto your work, but it can quickly backlash and a mob will form against you. They don't like people coming in there to blatantly promote their work/product. Which I think is unrealistic -- unless you really just want attention and like points through the Reddit system, EVERYONE who stops by there for an IAmA has some ulterior motive. But those Redditors, god bless 'em, take the integrity of the IAmA board very seriously. My thread snowballed but it just wasn't worth it. Maybe in the short term I sold a couple more copies, but it's not sustainable to rely on pissing people off and stirring up controversy. Your marketing and promotion should be provocative but not just for the sake of it.
Point being, I would do planning and preparation before jumping in with the Reddit sharks.