Last week, Feb. 2, 2007 the over/under number was 9, and the over hit.
Why the experts picked 9: It's a little cold today. By the time of services, the air should dip down to around 27 degrees. And on the other hand, a bar-mitzvah is coming up and perhaps he will show up like he did last week with his lovely grandparents in tow. The number may be a little low given that last week the over hit despite the rain, but we'll see.
On the halacha of counting people: In general, one is not supposed to count people. If you must, you do so indirectly. This reminds you that the people are not there for your purpose-- usually when you are counting something, you do so because you want to use it, or claim ownership of it. In the case of counting for a minyan, the idea is that we are all there for the purpose of serving God. Therefore, we do not count directly. Some employ the method of "not"-- i.e. "not one, not two, not three." I assume this reminds people that those that they are counting are more than numbers. Others employ the method of using Psalm 28:9, which has ten words. If you can recite the whole pasuk assigning each person a different word, then you know you have a minyan-- hoshia et amecha uvarech et nachaltecha urayem v'na'asem ad haolam. There is definitely a machloket, a disagreement, about the permissibility of counting people for good purposes. Rashi thinks its best to refrain from doing so, while Abravanel believes it is acceptible. In general we try and refrain from doing so to remind ourselves it's the people that count and not the numbers.