It's a good question TH - and you'll forgive me if the tone of my answer is a bit abrupt - it's not aimed at you.
No platform type is dead. Article sites are great, WIKI sites are great - even the odd forum profile and a few blog posts are fantastic.
The crap sites go. Article sites were culled after Panda in April 2011. WIKI's were spammed to death with idiotic "10,000 WIKI blasts"
Those that survive, monitor content, check for spam, perhaps have PR (and in quite a few cases are also D0follow) are great.
Google doesn't give a FLYING F^%K whether a site is wordpress.com, tumblr, blog, WIKI, article or "aunty nellies homemade cooking site"
If the content on it is good (it doesn't encourage spam), if it has a decent link profile itself (for PR) if it allows a static URL for user posted content (for tiered linking) and maybe if most of them are D0follow, then it's a good site.
What you might have is a shit linking profile if you are daft enough to order a "10,000 blast" of any specific platform type.
And it's those tools that spammed the living crap out of massive WIKI lists earlier in 2012 that killed off the WIKI boom. Loads of sites dropped in serps, got deindexed or so full of spam that the owners either ditched them or changed platform.
But guess what that means for those that are left?
Go on - do the "logic math" here. Have a guess what the common denominator is for most of the survivors?
That's right it means that, more than likely, they are GOOD SITES. Some are great. The crap has been culled, the spam palaces de-indexed, the ones with thousands of OBL's have felt the cold wrath of the Penguin, SERP positions destroyed etc.
Just like the article cull of 2011 - the WIKI cull of 2012 has left [in general] JUST THE GOOD SITES - ones that are harder to get links from, but if and when you DO get links they are worth far more.
Platform variation is as important in linking as anchor text variation
i.e
50 wikis
50 articles
50 WEB2.0
50 forums
50 blog posts
50 other random crap
= A great linking profile
300 WIKI sites and little else
= A shit linking profile
It would be nice if people would stop blaming "platforms" for their own lazy assed linking habits. Buying a "spam one platform type" tool and letting the f^%$r create a gazillion cookie cutter links doesn't work too well these days, but every type of site that fulfills the criteria (PR, static URL for link, mostly d0follow, allow content for context, nice if they allow more than one submission per account) above is a great place to link to as long as the overall linking profile of your site is diverse enough.
When people talk shite about "forum profiles are bad" or "blog comments give you negative SEO" I literally would like to reach into my screen and start knocking some sense around (and, as the few of you who know me know - at 21 stone (just under 300 lbs) and with less fat on me than a butchers pencil - it would probably result in some serious damage being done if I did - though mostly to my lovelyt monitor - so I think I'll leave that out

)
Put it another way. If articles are out, if WIKI's are out, then whatever the next "site de jour" is - that will be spammed to high hell inside 12 weeks and be out as well, so you might as well save your effort and not even bother OR understand that there is no such thing as a bad site to link from - but spamming the same site type over and over again will give you a bad linking profile for sure.
Scritty