However, there are lines you don't cross because 1) even competition should follow some rules of professional conduct, and 2) it opens the door for everyone to do the same thing to you. Representatives of Cryptic Studios crossed this professional line in the sand recently by going into City of Heroes / Villains (CoH/V) - their old product, which they sold to NCsoft - and, using PMs sent through the forums and allegedly through in-game message systems, attempted to lure players into the Champions Online (ChampO) beta test - their new product.
Here's a copy of the forum PM:
Hey <name>, this is Diamonds from Cryptic Studios.
We would like to offe...