Originally Posted by Desher

There wont be any tax forms that you need to file for contributions. other readers are correct in that you will owe taxes and penalties on only gains - unless the 529 beneficiary actually did incur higher education expenses of course
I have recommended contributing and withdrawing money within the same year for a lot of my....associates - though not for the reason of MS of course.

There will be a tax form generated listing the total DISTRIBUTIONS for the year. I'd keep the year end statement that reflects my contributions equal my distributions.

Things I'd consider:
Each states 529 plan does have a maximum (somewhere around $250,000). That's per state, per beneficiary. That is a cap on total account value. you can have $1,000,000 in contributions so long as your balance stays below $250,000 (for you big MSers who go big or go home)
You can be both the owner and beneficiary of the same 529 as long as your over 18.
Check for up front sales charges on the investments and any annual fees that may take away from you contributions.

So tax-wise - i'm not worried.
the 529 custodians (vanguard, schwab, etc) wont be a problem.
and let's just say someone does ask questions. "well i kept contributing to the 529 plan but my wife kept pulling the money out to shop and i didn't notice it until now."

As always, none of this is tax advice. do what you feel comfortable with.