Originally Posted by DoubleJ
I also wonder if one can get points for multiple concurrent promos, and what the allowable combinations may be, or if signing up for another promo invalidates the previous one. Or, like I've found with NW promos, if the first one signed up for invalidates any subsequent promos signed up for if in the same time period.
This a guess... but I do not think PC promotions invalidate eachother regardless of what the terms and conditions say. It would be too hard. PC has many points and miles promotions for members all around the world. They then target a specific group of eligible members either via mail, email, or Web links.
PC could write back-end scripts on their servers that, for example, invalidate promo code 9305 (10k for 5 nights) if the member successfully earns points for code 3172 (10k for 6 nights). However, they don't do this. With so many countries and members involved, the number and frequency of promos, and so many special cases, plus the risk of an error in the script, it would be extremely difficult to account for all of the potential scenarios.
Instead, PC assumes the vast majority of members do not read FlyerTalk and only know the codes for which they are given. PC is willing to take the loss on the few users who "over register" because that cost is far less than the time and effort involved in trying to make sure no one receives more points than they are allowed.