A short apology to everyone reading Daily Breadcrumbs off the LJ feed: I was fiddling with the settings yesterday and somehow refreshed the RSS feed, so that it republished all the recent entries. Once again, sorry.
The traditionally stated reason Laban was able to trick Jacob into marrying Leah instead of Rachel is because Leah was veiled during the ceremony and subsequent consummation. (Gen. 29:22-25) This is the source of one of the key differences between Jewish and Christian marriage celebrations. In a Christian ceremony, the bride is veiled until the end of the ceremony, in order to protect her from evil spirits and jealous friends of the groom. In a Jewish ceremony, the groom himself puts the veil upon his bride, and lifts it before agreeing to marry her. This is because Jews don't want a repeat incident of the trickery of Laban ruining a couple's happy day.