My mother (why the quotation marks?) loves recording videos and wouldn't dream of removing them from her phone/SD, even if she imported them to her computer. Filling 8GB is very doable. She'd be thoroughly confused once she did so.
Giving power users the option of moving things around is OK, but the phone shouldn't report that it's out of space unless all the storage mechanisms (internal and SD and anything else) are actually full, as opposed to;
> Today my phone said I was out of space, but it turns out I have plenty of space, but just not in the right place.