If we are to believe the information in the Google patent application, then the rate at which we increase backlinks to our sites is important. Keep the backlinks coming. Keep increasing the rate at which they come. Do not gain tons of backlinks at one time. Do not take a break from getting backlinks. Imagine a line graph such as the one below, where the line represents the number of backlinks you have obtained month to month, ever increasing. Sudden dips, or breaks in the line, could be seen as your page becoming less important. Massive spikes could be seen as an attempt to spam the search engine.