Don’t use Hubstaff, if not for the ethical issues, for the security issues
Hubstaff does not respect copyright! Their software is installing various GNU GPL and GNU LGPL licensed libraries without respecting the license of these libraries. The sourcecode was not offered at the same place and I didn’t see a written offer.
Hubstaff is using HTTP (not encrypted) for all the traffic! The application is sending the login and password in clear text. If you use Hubstaff at the airport, at a local coffee place, in a shared office, everyone can see your password and take over your account. The activities, notes and screenshots are transferred in clear as well. This means that everybody can look at potential confidential information sent from your employee to the Hubstaff server.
To make it worse, it appears trivial that your employees will send you wrong activity information and screenshots. In general this is a game your employees will win but Hubstaff gives a huge head start to your employees.
In short Hubstaff does not respect copyright law, they don’t value your data and they have not the slightest clue about security/privacy. No sane business will trust them.
Update: Hubstaff claims that starting from version 0.8.0 SSL is used for the connection to their server, they also claim that their GPL violations have been addressed. I have not verified those claims.