Some scientists really like the idea. I used to work with a guy who earnestly believed that any alien intelligence we encountered would surely be more wise and benign than us, because (basically) that's not a very high hurdle to clear. That was the extent of his argument. "We're nasty and brutish, therefore they must be better than us."
Yeah, the logic eluded me too.
Others, and personally I'd tend to side with this camp, think it's stupid and dangerous. If there's one thing we can learn from playing Civilization, it's that when two or more groups of people are interested in colonising the same patch of space, they will end up fighting each other. Since it's likely that these hypothetical aliens have developed through processes of biological, social and economic evolution that are not entirely unlike ours, it's reasonable to assume they know this. And if they do have any much better technology than we do, they'll use it to crush us like nuts.
So the best we can hope for, really, is that anyone who does hear the messages is even stupider than we are. In which case, I'm not sure there's much point in talking to them.
Not that that will stop anyone... Communication based on the assumption that the other party is a moron has been raised to a fine art in our times.
"Dear Organism, We have been monitoring your excellent planet for some time now, and we are really impressed with the range of topics you cover. We wish to purchase ad space from you in exchange for Earth currency denominated in the highly collectable 2009 Zimbabwean dollar."
"Dear ET, Earn money in your own time! This is not a pyramid scheme and is guaranteed 100% legal in accordance with current USPS guidelines!"
"DEAR THING: HOW ARE YOU AND YOUR FAMILY? I HOPE ALL IS WELL WITH YOU. I WRITE TO INFORM YOU ABOUT MY DESIRE TO INVEST AND TO BUY A HEXAPOD ON YOUR PLANET, AND I HOPE THAT THIS TRANSACTION WILL BE GIVEN AN URGENT APPROVAL AND WILL BE TREATED WITH THE STRICTEST CONFIDENCE."
Come to think of it, exactly what are those idiot scientists saying anyway? Are we spamming space already? If so, the aliens will have all my sympathy. Until about 0.3 seconds after their planetary bulldozers uncloak, that is.