I'm going to have to partially agree with Words of Wisdom on this one. People do know what crap is, even if they are one of the "casuals." You hardly need to be an expert in video games to know when you're not having any fun. And addressing your larger fear that shovelware will give "uneducated consumers the opinion that ALL Wii games are shovelware"," I admit it's possible that a person who repeatedly gets burned by shovelware will come to abandon video games as a whole in disgust.
However, I think the effect of this is far more limited than you fear it might be. I'm sure all of us have been burned by "shovelware" at some point in our lives, and I'm not just talking about in video games. I, for instance, would be a "casual" consumer of movies, plays, and other forms of entertainment. I've spent good money to watch good awful movies, see horrible plays, and read incredibly stupid books. But I'm still quite aware that my bad experiences can not translate into "ALL movies etc. must blow."
Granted, video games are much more shunned compared to those other media, so the chances that a person will play Ninjabread Man and tell himself that he's justified in having never previously played games is higher than my having a similar opinion about movies after watching, say, anything by Uwe Boll. But there's two things that mitigate this for the Wii. First, if many games' long legs are anything to go by, a lot of people are purchasing their Wii games by word of mouth, or after trying them at a friend's house, so there's a pretty good chance that someone who bought a game at least knows what they're getting into. Less theoretical is the fact that every Wii comes with one of the best games ever made, Wii Sports. After playing that for hours, people will know that quality games do exist, and I submit that they're less likely to stop playing games after one or two bad experiences than you may think.
That said, if we never see another "Cars" again, I won't complain.
Edit: My tortoise-like typing speed strikes again!