In addition to the arguments listed there the thing that bothered me most about it was that it imposed a straitjacket on the editorializing of any article that contained spoilers, you now had to bend over backwards to partition it into spoiler and non-spoiler sections.
I still think though that they should do a better separation between the actual information and the story elements though.
Also, who should spoiler warnings in an article about a TV series benefit? People who haven't seen the latest series? People who haven't seen it at all?
Should the summary say nothing about how Walt turns to crime (which wasn't apparent to me when I started watching it), and instead describe Breaking Bad in vague terms as the struggles of a New Mexico man to provide for his family?
Spoiler warnings are inherently at odds with writing a succinct and accurate summary of a given subject, which is what Wikipedia strives to do.
Other commenters here are right, if you don't want something spoiled for you then simply don't read encyclopedia articles about it.
You wanted some information about the structure of the aired episodes, there's plenty of TV-guide like sources for that that aren't encyclopedias.