Can I increase difficulty and drops through a command?

In Diablo 2, if you wanted a higher difficulty in single player, you could type /players 8 to make the game scale the difficulty, experience, and drops to what it'd be if there were 8 players in game.

Does Diablo 3 have an equivalent? I was not able to find anything in the D3 FAQ, so I would suspect it does not. Are there any methods for increasing the difficulty/exp/drops other than playing at a higher difficulty level?

This system is being added in patch 1.0.5 (it is referred to as Monster Power). Details are available on the official Diablo III blog .

You first need to select "Enable Monster Power Selection" on the game play tab of Options. You will then be able to select your desired monster power level from 0 (off) to 10 in the Quest Selection interface.

Here is a quote from the blog regarding the "/players 8" asked above.

Similar to the "Players X" command in Diablo II, Monster Power gives Diablo III players the option to increase the health and damage of monsters according to different "power levels" -- and in return, they'll receive scaling bonuses to their adventure stats (including experience, Magic Find, and Gold Find) as well as more drops.

Here are some of the charts as of 1.0.5:

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UPDATE: An updated version of the Inferno chart for 1.0.7: http://us.battle.net/d3/en/forum/topic/8920082006

There is no single player per se in Diablo 3. Every game is a session running on a Blizzard server and can potentially be joined by other players.

A technique like setting the number of players to increase drop quality/difficulty/experience would not have made much sense, and therefore is not available in Diablo 3.