Painting the brick won't necessarily ruin it, however it will take some work to remove the paint, which can add up to some expense. Perhaps covering it with drywall is a better alternative. Have you thought about maybe being a little creative and leaving some brick exposed by covering just a portion using drywall, creating more light and retaining some character? This opens up a world of possibilities and keeps the option of removing the drywall if you desire.
Just some food for thought.

Kirk

If you are going to paint the brick white i suggest you use an oil based paint which when it comes time for removal will be able to be done a lot easier than if you used a a latex (water based paint) since brick is porous and latex seeps right into the brick and is very difficult to remove. Good luck

I agree with the suggestion of using drywall to cover it instead of painting it. Most brick is so pourous that it is virtually impossible to really strip it perfectly. Of course, everything comes down to how much it will cost, not whether it is impossible, so the translation is that it will be a labor-intensive, costly, expensive job to remove the paint if you paint the brick.