The Bilderbergers are more secretive about their meetings, so in their case the paranoid are simply filling in the information void. If they won't tell us why they're meeting, they must be orchestrating a worldwide takeover, right?
Why it's Retarded:
The underlying claim behind both is that these groups of wealthy men have been working to create the infamous One-World Government that you'll see pop up in most of these conspiracy theories. They want a totalitarian regime that will enslave all of mankind, all at once.
Of course these guys have had decades to establish their plan, but instead they apparently opted for plan B, One-World Clusterfuck. Europe hates America; the Middle East is more fucked than a German whore on coupon day; all China cares about is exporting delicious lead paint; and North Korea is still run by that crazy fucker with the big granny glasses. It's almost as if the result of their "one-world government" conspiracy looks exactly like the random chaos of geopolitical events we've seen for the last few thousand years.
"We've got them right where we want them."
Don't get us wrong; we suspect both of these groups would like to rule the world (so would we, in fact). But in the grand scheme of political and economic power worldwide, a few hundred important guys basically amount to a fart at a Motorhead concert. It's too much to assume that even within the groups that there is agreement about what the Master Plan should look like, since they're made up of people from different countries, political parties and competing corporations.
But what conspiracy buffs are doing is taking any world event and retroactively declaring it to all be part of the Secret Plan. Economy booming? Of course, that's part of the secret plan to make the corporations control all wealth. Economy collapsing? Of course, that's part of the secret plan to destroy capitalism.
If it rains, it's because the Trilateralists want a flood. If it doesn't, it's because they want drought. And both are held up as proof after the fact, so as far as they're concerned, they've got proof out the ass.