This New York Times article reports unrest and tensions along the Brazil-Paraguay border. Paraguay has a new populist president, Fernando Lugo, a former Roman Catholic bishop. His primary constituency is among the poor, who are agitating to take back land from Brazilian farmers who have farms in Paraguay. Meanwhile, the article reports recent Brazilian military maneuvers along the border, making Paraguay nervous.
Paraguayans have every right to be nervous. Brazil has 28 times the population of Paraguay and 21 times the land area. Compared to giant Brazil, Paraguay is militarily (and economically) insignificant. I presume the Brazilian army could occupy landlocked Paraguay in a weekend, and I presume Paraguay knows this.