Fitbit today sent out an email to users that have integrated their accounts with Microsoft's HealthVault service, stating that the company will no longer support it. After September 12, your data will continue to be available from your Fitbit dashboard.
HealthVault is meant to be a sort of central hub for all of a user's health data. The problem is that few people actually use it. Even Microsoft's Health app - which offers similar functionality to a Fitbit, using data gathered from a phone or a Microsoft Band - doesn't integrate with HealthVault.
Fitbit on the other hand will need to keep ahead of things like this if it is to continue to grow. Resources would likely be better spent developing new products than supporting services that very few people use, such as the two products that the company has already announced this year - the Blaze smartwatch at CES and later, the Alta fitness band.