InDiSent, to answer your last question: no, you should not have full control of everything by default. That's what the superuser or "root" account is for. Using the root account is a security risk and even a novice user can damage the OS with so much authority. Most virsuses and other malware will run at the same privilege level as the logged in user. If you are running as root, then the malware is running as root. The word "rootkit" comes from this -- only a root user should be able to install one.
Giving every user the equivalent of superuser access is one reason (of many) that Windows has been so vulnerable to infection. UAC in Vista was added to reduce this risk. From my understanding, the Mac OS, which is based on Unix, keeps the root account hidden from the system owner by default. That's one reason Macs are less vulnerable to infection. Finally, if you *really* know what you are doing, and accept the risks involved, you can make yourself a full-time, always-at-risk superuser as LH has done.