Because clicking that “Poke Button” link yourself is just too damn hard.

repoke.js

var repoke = function() {
    var pokes = 0;
    Array.prototype.forEach.call(
        document.getElementsByTagName("img"),
        function(el) {
            if (el.className !== '_3-8_ img')
                return;

            var parent = el.parentNode;
            if (parent.innerHTML.indexOf("Poke Back") == -1)
                return;

            ++pokes;
            parent.click();
        });

    if (pokes == 1) {
        console.log("Responded to 1 poke.");
    } else {
        console.log("Responded to %d pokes.", pokes);
    }
}
window.setInterval(repoke, 1000);