To quote the wiki:
When the player crafts blocks of diamond, emerald, gold or iron and places them in a pyramid shape beneath the beacon block, it will emit a beam of light into the sky and can apply temporary buffs to the player once activated.
... To activate it, place either an iron ingot, a gold ingot, an emerald or a diamond into the GUI slot.
So it actually isn't that hard in 1.3 to just do a bit of trading with villagers, get lots of emeralds, then make emerald pyramids and use emerald to buff you. Note though that there isn't yet a way of crafting the beacon block (and may never be) and that
Effects will be applied to the player while within a radius of the beacon, with larger pyramids giving larger areas-of-effect. The radius is approximately 16 blocks, 24 blocks, 32 blocks, and 40 blocks from the smallest pyramid to the largest. The radius takes the player's y-coordinate into account.
... The item will be consumed and the beacon begin providing the power to nearby players when "Done" is clicked.
So the range is limited and anyone within that area of effect may be buffed.
Anyone willing to test this at home?