Privacy laws governing the use of information gathered online differ from nation to nation, and the few that exist are new and untested. Some service providers have tried to sell information about their customers, and have been met by a great deal of flak. If your privacy is truly important to you, you'll think twice about volunteering information via online questionnaires and the like. Developing a database is usually what these are there for. The word virus makes everyone nervous, whether you're talking about computers or the common cold.
Viruses are out there, although most are fairly benign.
It's prudent to have the latest virus-protection software installed on your computer, and to run any downloaded programs through it before they go on your hard drive. Until recently, when a newbie asked if hackers could invade your home computer when you were hooked up to the Internet, the standard answer from old timers was derisive laughter. However, events in the spring of 1995 proved that it can, in some special cases, be done. He didn't boast for long, though, because the wronged party immediately joined the manhunt for Mitnick, already on the run from the FBI, and helped them make the arrest. Mitnick'll be cooling his heels for a long time, but there are more where he came from.