I've done it previously (last year) and hadn't run into any issues. However, there's a lot of recent talk about people having their accounts closed for using promotion codes they were NOT targeted for. I stopped doing it probably about 5 months ago... hoping they aren't going back that far... I'm not doing it anymore. I have too many points (that I plan on using this year) to risk it...
I'll throw my experience out there. Been an IHG member for 10 years or so, but very little activity. I had one unqualified stay last year but my most recent points-earning stay was in 2011.
I recently switched companies and my current one lists IHG as their preferred hotel chain. I had to travel for work last week and dutifully loaded up all the promo codes I could before booking a 5 night stay. My points have now posted from the stay and I received a modest 17,114 points. Checking the details on the stay, there were 5 other promo codes I signed up for and show in the account that did not register as completed. Also interesting is that three of the offers that did not credit show a status of 0% while the other two show no percentage at all.
I can't comment on whether this behavior is normal for times past or not. But I'd much rather them not give me points for offers I wasn't targeted for than close my account!
My account was locked down for entering various promo codes even though I never booked a stay. After calling, they unlocked my account but warned they would shut me down if I used unauthorized promo codes in the future.