Kam has very good points. Basically, its like acts 6:12 "All things are lawful for me; but not all things are advantageous." Also the principle found at 1 Cor. 8:4-13 applies here. the point there is basically, don't stumble your brothers.

So while myspace might not, in itself, be wrong. It'd be better to set a good example, and avoid the site all together.