I would say that most bloggers provide a reliable information about sign-up bonuses - if they aware about better offer they tell it specifically. From my experience, only Dan from dansdeals.com usually does not post better offers - he usually provides his links and even recommends to apply for 3 cards simultaneously from the same bank (I think to get a maximum referrals). If you read his blog recently, he urges to apply for Continental card (25K sign up bonus) as fast as you can and does not say that if you do so, you will not be able to get a bonus for United Explorer card (50K bonus). For example, Darius from MMS explicitly tells not to apply for Continental card because of this.