Looks like trading sports bands is a no go because it is 3 pcs, not 2 full bands. TechCrunch has the article.
http://techcrunch.com/2015/04/10/psa-sorry-those-apple-watch-band-swapping-sites-arent-going-to-work/?ncid=rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Techcrunch+%28TechCrunch%29
http://techcrunch.com/2015/04/10/psa-sorry-those-apple-watch-band-swapping-sites-arent-going-to-work/?ncid=rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Techcrunch+%28TechCrunch%29