Full disclosure off the top: I worked in an Israeli olive factory for a year when I was in high school. One of the entry level jobs for rookies was "the olive line" where workers sat and watched the product roll past them on a conveyor belt. The job entailed grabbing those olives that looked defective and removing them from the belt to ensure only nice looking olives made it into the cans and jars to be sold. Even with headphones tuned to the rock radio station in Jordan it was mind-numbing work but it did teach me one thing: the size of an olive.
I mention this because, like clockwork, the issue of how much matzah to eat at the Seder next week, has once again surfaced in the Jewish blogsphere. This amount is, al pi halacha, the amount of an olive's bulk of matzah, a k'zayis. Naturally Jews have to argue about anything so when it comes to this issue the argument is: how big is an olive?
You'd think that it would easy to end this discussion. Olives come in a few varieties so find the biggest one and say "That's how much matzah you have to eat". This is the one solution that, to my knowledge isn't considered viable by most people. Instead we have a notion, based more on opinion than any real historical fact, that olives shrunk significantly in size somewhere in the last 2000 years which means our current k'zayis is way below the minimum amount necessary to fulfill the mitzvah of achilas matzah.
Rav Natan Slifkin has already dealt with this issue at length and I have nothing to add to his scholarship on the matter. There are definitely different opinions and those of the great poskim of the last 1000 years cannot simply be dismissed due to lack of historical agreement with their positions. They are the gedolei Yisrael upon whose words we rely. But when people distort their words or amplify them we are in a worse position.
For example, the recent article at Yeshiva World by Rav Yair Hoffman does exactly that. Rav Hoffman starts by presenting an opinion, that of following the maximum number of authorities with divergent opinions when performing a specific ritual, as a near universal practice. While this occurs quite frequently there are many other times when we pick one authority or a minority and go with them. Sometimes who we side with changes depending on extenuating circumstance in different eras. Yes, fulfilling as many opinions as possible is definitely desirable but not when it leads to bizarre behaviour or contortions in logic to justify itself.
It seems, according to Rav Hoffman, that not only do we have to conform to the ever-expanding definition of k'zayis (once the size of an olive, eventually some bright young posek somewhere will declare it to be half a canteloupe) but we have to eat twice as much of it and all in two minutes!
Add to all of that the fact that the burnt oversized crackers we eat are not really traditional matzah but a result of hard necessity a few centuries ago. Soft pita I could see shoving into one's month at a reasonable rate but spit-absorbing crackers? Won't happen.
Here's my suggestion: Rav Chaim Volozhiner, zt"l, is, in all other respects, an important posek and a huge Gadol in the chain of halachic transmission. If he says that an olive is an olive then I think we can rely on his formidable knowledge in the matter. After all, he and his mentor, the Vilna Gaon, ztk"l, are not known for a lenient and superficial approach to p'sak.
There is a further reason to take this position, one that is often forgotten by most folks in their zeal to do "the right thing". The Torah tells us to rejoice on our holidays. Now I've heard it said that this only applies to Sukkos which is called "chag" by the Torah which means that we are allowed to make ourselves miserable on Pesach. I'm not sure that's really the optimal understanding of the verse. We are meant to enjoy Yom Tov, the better to appreciate the bounty the Ribono shel Olam has given us, the better to allow His splendour to interact with us.