Mana curve?  What mana curve?

This is a quick, nasty little proliferate deck that's cheap to build, cheap to play, and hardier than you might expect under fire.  You want to get your first infect damage early - Glistener Elf, Blighted Agent, and Ichorclaw Myr are all at your disposal to this end.  Use your Mutagenic Growths liberally - turning an initial poison counter into three is very convenient as the game goes on.  After that, block freely.  Get what infect damage you can, but don't be afraid to throw away your agents to get a valuable -1/-1 counter on a creature.

Once your opponent has a poison counter, use the Thrones with reckless abandon.  Ichor and Mycosynth Wellsprings exist to die.  Burn 'em quick for proliferate and draw/land power.  You won't need the land, most likely, but it'll lessen your mana dilution and give you better chances of swarming with infect.  Use your Necropedes and Contagion Clasps against creatures.  You probably won't pay the four mana for the clasps; I tend to burn them with the Thrones instead, unless I've had a good run of Mycosynth Wellsprings.

I keep Elixir of Immortality in the sideboard to combat the fast battle cry deck and the mill deck.  Withstand Death is a nice addition if your opponent is relying heavily on direct damage or black destruction spells, but it is also useful for blocking purposes.

For the spendthrift player, swap out some lands for Inkmoth Nexuses, and feel free to switch some of the cheaper creatures for Putrefax.  I like Phyrexian Metamorph in this deck as well, especially if your opponent has some big creatures/artifacts that can be skillfully copied.