Confused. Can we send inlude an affiliate opt out electonically by posting on website to those customers who have agreed without requiring an acknowledgement?

No. You must comply with E-sign to provide electronic disclosures.

Gulp. I thought for affiliate marketing opt out we did not need to comply with E-sign to provide the opt out, particularly if combining with privacy policy notice?

§ 222.26 Delivery of opt-out notices. 62961
http://www.bankersonline.com/topstory/72fedreg/72FR07-5349.pdf

From the page you reference:
(2) By electronic means. (i) The optout notice is provided electronically to the consumer, such as by posting the notice at an Internet Web site at which the consumer has obtained a product or service. The consumer acknowledges receipt of the electronic notice. The consumer is given 30 days after the date the consumer acknowledges receipt to elect to opt out by any reasonable means.

#3 mentions internet as well, but it is in conjunction with an electronic transaction.