What are the disadvantages of having a computer??
None so long as the computer used correctly; however many people do not do that. Check these sites.
http://en.wikipedia.org/wiki/Cybercrime
http://74.125.93.132/search?q=cache:__NKh_3f2CYJ:www.calstatela.edu/its/docs/pdf/section502.pdf+illegal+use+of+computers&cd=1&hl=en&ct=clnk&gl=us&ie=UTF-8
http://www.cityu.edu.hk/csc/netcomp/jun2005-4.htm