American Express Membership Rewards - MR points to SPG points

This has surely been asked before but I can't find it on the board so I'll ask again...
On the AMEX SPG credit card site it says you can transfer your AMEX MR points into SPG points. There must be some way of stopping you from just transferring 20,000 MR points into your SPG account and then proceed to deposit them into your choice of FF account to get their 25% bonus. I just haven't found the proper fine print yet but I just thought I'd take a short cut and ask here about this. Maybe MR points don't transfer into Starwood points at a 1:1 basis in the first place?
Thanks for your insight.

If I recall, MR points in the US MR program transfer at 3:1. I think that is the reason this does not happen.

If I recall, MR points in the US MR program transfer at 3:1. I think that is the reason this does not happen.

Yes, this is precisely the reason why nobody does that - even with the 25% bonus you would be losing loads of miles.

I knew there had to be a catch there somewhere. Thanks for the help.

If you want to transfer your MR points to Skymiles you can take advantage of the 20% bonus now.

http://www.delta.com/skymiles/ways_to_get_miles/transfer_miles_partners/transfer_miles_lto/transferrewards/index.jsp