Assume that I would like to join an affiliate network, but I can't find any reviews of them and Alexa shows that their domain exist for 2 months. In this case I should probably wait until they gain some reputation, however waiting is not good for my bussiness.
How can I verify that some online company really exists and is trustworthy? Don't they have to be registered/verified somewhere?
The Better Business Bureau accredits online companies as well which would be a good starting point in checking how trustworthy a company is. A few other things you can do:
1) Does the company have a legitimate address? P.O. Boxes should make you a little wary. Check the address on Google Maps and make sure it really exists.
2) Does the company have a valid phone number? Do a reverse lookup on the number to see if it is "unpublished". That is another red flag.
3) The fact that the company hasn't been in business for more than 2 months should also make you wary.
Another thing you may want to do is ask for references, both customers and other affiliates.
Then you can speak with the other affiliates to see how it is going for them. Are there problems with shipping, payments etc?