When pressed, Israeli officials said that they believed they had killed about 200 Hizbollah fighters during the first two weeks of the fighting. But now Western journalists in Lebanon are reporting seeing dead civilians who were apparently Hizbollah members. The Israelis probably do have a better idea of Hizbollah losses than they are admitting, because Israel maintains a network of agents inside Lebanon. They know that the military wing of Hizbollah is not large, with only a few thousand trained fighters. Once that crew takes serious losses, Hizbollah will have to rely more on less effective part-timers. Israel really wants to know when that point is reached, for at that point new tactics can be applied, that will speed up the destruction of Hizbollah. So, for Hizbollah, secrecy is a matter of life and death.
Israel, being a democracy, with a free press, every military and civilian casualty has to be reported. So Hizbollah knows how their enemy is doing. But the Israelis are so much more powerful militarily than Hizbollah, that precise knowledge of Israeli losses is not all that important.
The current war in Lebanon involves keeping secrets to survive, and win. Take, for example, casualties. Hizbollah is a totalitarian organization, and does not have to release any casualty figures. In fact, Hizbollah has an interest in not letting the Israelis know how many Hizbollah operatives are being killed. That way, the Israelis won't know how badly they are hurting Hizbollah, nor how effective the Israeli tactics are. In addition to saying nothing, Hizbollah can also get away with lying. Since Hizbollah fighters don't wear uniforms, many of the Hizbollah dead can be reported as civilians. This makes sense in terms of propaganda, as Hizbollah wants to portray Israeli attacks as unwarranted attacks on innocent civilians.