Reading "light and darkness" in the rule compendium 79 it appears clear that someone can hide even in an area of bright light.
In an area of bright light, most creatures can see clearly. A creature can’t hide in an area of bright light unless it is invisible, has concealment, or has cover.
A shadowdancer with Hide in Plain sight, can hide in an area with light, as long as there is a shadow.
Some backgrounds on why I ask this question:
The description of HiPs (e.g. shadow dancer) does not specify the size of shadow needed to hide. Following this line of thougths, even the shadow produced by an ant inside an empty room, whose the ceiling is affected by the spell light, would be enough for the rogue with HiPs to hide in plain sight. From this line of thoughts we agreed that any spell that makes light is useless to spot someone using HiPs as they specify that the light bursts from the target.
In our party we concluded many years ago that there would only be one situation in which there would not be any shadow to hide, this being an empty space that has light coming from any direction.
For such reason we agreed to limit the versatility of HiPs and house ruled HiPs saying that the size of the shadow would need to be at least half the size of the player who uses HiPs.
Said so, I only recently imagined that in case there were no shadows of the needed size a rogue could possibly create shadows by casting light on themselves move close to someone or something, even quite small, as "light" would then propagate a considerably bigger shadow...