Why do many people say כאלה with the Baal koreh during the leining of pesach? (http://www.collive.com/show_news.rtx?id=31122 confirms what I find to be true across the spectrum of different kinds of shuls all having some people who feel this is a minhag.)
I heard once that this is based on the Shaarei Efraim 8:24. The Shaarei Efraim discusses what one does if they skipped the verse beginning with כאלה. Thus there are those who out of concern that it may be missed that say it out loud.