first off, we have claudius, hamlets uncle, calling in rosencrantz and guildenstern because they know him well and may so be able to help "fix" his problems. coming from a poisoner, that makes me quite nervous.

secondly, and i quote,

"Both your majesties
Might, by the sovereign power you have of us,
Put your dread pleasures more into command
Than to entreaty."

translation: you could just force us to execute your command(s) without question rather than politly asking us. again the whole execute thing...getting dangerously close to the truth but this time its rosencrantz saying it.

what im trying to get at is that claudius is very thinly veiling his intent to have hamlet killed, and would have succeeded had his letter stating, "there bearer(s) of this letter(s) is to be immediatly executed" or somthing to that effect got into the correct hands. we can also assume that claudius would have had rosencrantz and guildenstern killed shortly afterwords had he succeeded with hamlet

the amount of cunning that goes about on all sides is really rather remarkable. polonius is being cunning by trying to trap hamlet, the king is doing the same, but , wily beast that he is, hamlet still has them falling over themselves and into his own traps.