1. Pyramid scheme ? most of there program use the pyramid system which basically say that the person that invested first has a better chance to earn than the people after him.

2. Scam - these days almost every one can open his own investment site using a legal or illegal script, it's hard to spot a scammer but there are some ways to check it.

3. Luck - think of this as a gamble you win some you lose some.

I am using a very simple method to invest money on the internet

How to spot a scam?
1. License check - today its easy to get free license, many scammer use
It in order to check for a hyip script license goes to
goldcoders.com/?page=checkdomain
This company sells hyip script and here you can check the hyips domain.

2. A scam site usually will buy for his host or domain for a very short time you can check its Expiration Date in site like this:
who.godaddy.com
If you see he paid for only one month that should light your bulb.

3. The design - cheap and ugly doesn't point it's absolutely a scam but you better think twice, scammer want to invest the minimum.

What to do before investing?
After you check for scam signs comes the part of research.
Check the program on big sites and money forums like MMG or GPF and see what the other investor has to say about it.

Check the monitors, these are sites the monitors the investment site by invest in them, the sort them by their status (pay, pending, problem and scam) and by the investors votes.

Monitors are very good to find some new programs to invest in.
Remember, always check 4-5 monitors, there are many on the internet some good some not, compare the information.
This a good one I check everyday
http://www.thehyips.info Also this site has <---****HYPERLINK****--->"http://www.thehyips.info/"> HYIP forum where you can ask your questions.

How to choose ?
There are many options for investing high % low %, daily, weekly or monthly.
The high % will not last long when it's a hyip.
Auto surf usually last longer statistically mostly because it's easier and cheaper to open a hyip so most of the scammer concentrate there.

Some rules about investing
If you choose a hyip with a high % for instance 150% in 3 days invest only on the first day, about 99% of these are scams but you could earn if you are on of the primary investor.

Many hyips now use the round system, the will keep on pay till they cover 90-95% of the investors money, after that the round is over and they use the money for advertising, if you want to participate in a round invest only in the first day of the round else you are throwing away your money.

* don't spend all at once ? always make a test spend, if an auto surf upgrade costs 10$ don't buy 1000$ spend 10$ and check it, are they paying ?, how fast ?
See if you like it because there are many good ones today.

Only after you made a test spend begin investing the big money.