On all of my machines, the blink is very slow and there are good portions of the time where the entire thing has blinked out. If you want it to be obnoxious, it should be in a very high contrast color, possibly into the realm of interference, it should blink fast, not slow, and it should never be totally missing.

Another idea would be to have an interstitial page that forces you to click a button or link to actually get to a page where you can enter data.