Symptoms of problem gambling are:
1) A preoccupation with gambling
2) Reliving past gambling experiences
3) Taking time from work or family life to gamble
4) Concealing gambling
5) Feeling guilt or remorse after gambling
6) Borrowing money or stealing to gamble
7) Failed efforts to cut back on gambling
8) Lying to hide gambling
Personally, i don't see the initial idea of gambling as "bad" for most people. When it becomes an addiction however, it can be ruinous. Apparently gambling addiction is closely related to other substance abuse addictions and can occur in certain people more than others. Those at risk are:
1) Those that start gambling at a young age
2) Men are more prone than women
3) Those with biochemical abnormalities, particularly Dopamine and Seratonin have been linked to gambling addiction.
4) Those whose parent's gambled
5) Those who live close to a casino etc.
6) Those sufering other mood or personality disorders
Check out the links for more info.
http://www.ncpgambling.org/http://jama.ama-assn.org/cgi/reprint/286/2/260.pdf
http://www.nlm.nih.gov/medlineplus/gambling.html
http://www.mayoclinic.com/health/compulsive-gambling/DS00443/DSECTION=8