I see no problem with weighing yourself every day or multiple times a day, but you have to understand measurement error and noise and know how to get rid of that. There are many source of error and noise out there. First, most consumer grade scales are only precise to +/-0.6 lbs. So while they imply accuracy to the 0.1 lb by putting the tenth of a pound on the display, they really only work in 0.6lb increments. I know in the morning I either weigh 177.6, 178.2, or 178.8, but nothing else in between. Another source of error is a pint of water weighs 1lb. I know I can drink a pint of water in about 3 seconds after a workout, and it's so easy to be + or - a pint or two of water at any given time of the day. So you really can't say "I gained/lost 2 pounds today" because yesterday you could have been a pint low on water and today your a pint high.
There are many strategies to this, I always just round my weight to the nearest 5 lbs, because anything else isn't meaningful when you count all of the errors and noise.
Someone above mentioned doing a running 5 day average, that's also a very good method. Roughly, if you average N data points you get sqrt(N) more accuracy in your result.
But remember, todays measurement should count more than last week's measurement, so a really good way to do this is to use exponential decay averaging, you can look that up in The Hacker's Diet (http://en.wikipedia.org/wiki/The_Hacker's_Diet), most of what he says is crap (calories in, calories out nonsense), but he understands measurements, so it's a good start.
Though, really in the end the MOST important thing is how do you look, feel, and perform (courtesy Robb Wolf), the number on the scale is just a number and doesn't tell you very much. I just use it because I'm a data freak, I know that if I start to be consistently over 180 lbs, that it's time to start cutting back on the macadamia nuts, and if it's under 175 I can be less strict. But it never affects me emotionally on any given day. It's just another input.