Magic Find is a contentious issue with Diablo III players. If you're unfamiliar with the concept, Magic Find is basically an attribute which boosts your chance to find better items.
Due to the way it currently works, it's not uncommon for players to carry two sets of equipment in their inventory and swap out their regular gear for Magic Find gear shortly before they kill an elite pack, champion, or boss. Blizzard doesn't feel that this is a problem for the economy, but players often report their dissatisfaction with having to swap out their equipment simply because it's a major hassle to do so, and the benefit it simply too large to ignore.
As such, Blizzard is looking for a solution, and they want your input. The developers have come up with a number of potential solutions, including setting a cap on Magic Find, having MF slowly adjust over time instead of instantly coming into effect, setting an average MF% based on your score over the last five minutes, zeroing out MF% for three minutes after a gear swap, or having item swaps interact with Nephalem Valor.
You can read the options in detail at Blizzard's own blog, where you're welcome to submit your own opinion on the matter or go with one of their suggestions.