Dustin Curtis did an interesting experiment with a short call to action at the bottom of his pages, asking users to follow him on Twitter. Comparing the results shows that direct, but informally worded calls to action, and (ugh) using a literal call out like the word "here" had a pretty significant impact.
As the forcefulness and personal identifiability of the phrase increased, the number of clicks likewise increased. "You" identifies the reader directly, "should" implies an obligation, and "follow me on twitter" is a direct command. Moving the link to a literal callout "here" provides a clear location for clicking. I tried other permutations that dulled the command, used the word "please" in place of "should" and made the whole sentence a link. None of them performed as well as the final sentence.
At the very least, the data show that users seem to have less control over their actions than they might think, and that web designers and developers have huge leeway for using language to nudge users through an experience.
Would you come to the same conclusions? Read the complete article here. ;)