You should always be careful when handing over usernames and passwords to programs downloaded from the internet. 99% of the time it will be fine but sometimes it could lead to ruin. Not true? Then visit Coding Horror and read about how a programmer was hiving users Google e-mail passwords. Now think how many people use the same password for everything. Scary.
If you fall into the group of one password for all sites, try 1Passwd (not trying to be ironic). Great product which should help protect your many online accounts.