Recently, a local yeshiva had publicity flyers put up in the community that a certain rabbi from Israel would be the "Noem HaKavod", the guest speaker, at their annual dinner. To my great dismay, the rabbi never came to speak, but a video of him was shown at the dinner. Is this proper practice and if not, why do yeshivot who are supposed to represent unadulterated Torah, condone such practices?

Misleading advertising is prohibited as part of "onaat devarim". If someone purchased a seat for the dinner based on the assumption that he would be in the physical presence of the speaker (one would guess however that those who attended came to support the institution) the prohibition violated by false advertising would be even worse. In that case, the attendee might claim there was a "mekach taut"- and ask for a return of part of his money. Perhaps the rabbi intended to come and was forced to cancel at the last moment.