Who has access? Who owns it (don’t make an assumption here))? How will it be delivered back so you can move it to a competitor’s platform? Do you need to buy a proprietary (meaning, expensive) tool to extract the data? Who handles problems?
Who maintains the documentation over the years so you actually know what that database looks like and exactly what each element means (because that changes too)? This borders on the geeky but X may not always and forever mean X, or maybe now its X+2. Maybe X is now alpha-numeric whereas it started out as numeric only.