Whitey - 11:10 pm on Mar 22, 2013 (gmt 0)
Host crowding : [ perhaps ] To severely cut off or curtail a brand that pays you is unwise aka "to bite the hand that feeds you". Providing 2-3 additional listing helps smooth that relationship.
@Tedster - the NEEDS issue is spot on IMO
It drives a perception that organic traffic drops can do damage to those relationships. Google would want to do all possible to ensure that they look after their brand customers and their associated users who use the SERP's.
By default, if you can't pay as part of your overall marketing mix, to drive brand signals you won't rank. There is an indirect link IMO with high volume market verticals IMO