One of the database fields that the ASP.NET Membership provider manages is the "LastActivityDate" field. We are attempting to utilize this field to determine the last time the user was online. Yes, I know there is a LastLoginDate as well, but that is just that a Login date. Anyway, getting back to LastActivityDate, it seems that this field is being updated at random times and not by the user. We know this because it is happening to user accounts that have never logged in and blocks of users are getting this field updated at the exact same time.

So the question is, is there any reason why the ASP.NET Membership provider would be updating this field at random times? Or is there possibly some other environmental culprit here? This is a hosted web site, so I'm wondering if there is something in the hosting environment causing this.

Any pointers would be appreciated.