The way I understand it, it's not casual gaming that's causing the problems. It's Zynga personally.
Honestly, I enjoy casual games once in a while. PopCap created fun, entertaining games that required skill, strategy, and/or reflexes in order to win. Most of PopCap's library is fully original and a credit to casual gaming. Zynga, on the other hand, is treating games like cocaine. They give you a hit for free, but to get anything better requires "just a small fee"... and then another, and another... Zynga doesn't make games, as such. They make glorified slot machines.
They also, as has been pointed out many, many times across all of the posts, have no original games. Like slot machines, they put different pictures on the exact same mechanisms. They outright copied other people's games (and in some cases, their own games. see Mafia/Vampire Wars, FarmVille/YoVille) and put it exclusively on Facebook.
The only thing they added was the requirement of bothering your friends to play so that you can get something in your game. Not even World of Warcraft's cult-like status actually REQUIRES you to spam and beg, and harass your own friends in order to win. As such, more and more are drawn in to a (lets all face it) boring, but shiny experience. It's a brilliant marketing tool, actually. They've successfully manufactured a drug that requires your friends to be using in order for you to keep from losing your buzz. THAT'S what I object to. That and the owner's blatant disregard for his customer's complaints, and a thinly-veiled attempt to look good by pretending to send money to Haiti. Seriously, it's not enough to scam your customers, you have to put false charity on top of it? Despicable! But I digress...
On the topic of WoW, one might argue that MMO games have a similar effect. It's true that most of the games do require human interaction for the higher-level content. But what you are drawing them in to is a rich, fulfilling experience, similar to watching a great movie or reading a good book together. The experiences are literally shared. (Seriously, I invite all of the Farmville players to join a book or movie club and see what kinds of experiences can be achieved in real social networking.)
The PopCap people are right. Casual games CAN be good for the gaming industry as a whole, as long as the developers don't forget their primary audience (namely us). I say let them do their things. But Zynga is toxic, even to casual games. If they don't have a major reform in attitude, the entire gaming community, casual AND hardcore, could be in serious trouble.