You take a high enough resolution image, and use the Stamp Filter in Photoshop, playing around with the settings until you've got that stencil-look with the people. Then you would place them over the toned background and add your text.
Or, in Illustrator, you would place the image(s) of the people, and use Live Trace, adjusting the parameters to be black and white, and play around with it until it looks like you want it to. Then, you would draw a colored square, and place it behind the images, add your text, and you're done.