This is most certainly not the case, and partnerships in affiliate and internet marketing can prove to be incredibly lucrative.
The reasoning behind such partnerships is that, for example, while you may be good at developing websites that get good search engine rankings, you are not very good at writing compelling sales copy. So, you have a lot of people come to your site, but you don't get a lot of sales.
Let's say that another person is great at writing sales copy, but doesn't get a lot of people to his site because he doesn't know much about SEO, but those that do end up at the site tend to buy.
On your own, you are both getting low sales. If you team up, however, you can generate more profits. Of courst the profits will be divided between you, but your percentage will likely be higher that you would have achieved on your own.
Partnerships in affiliate marketing are also a great way to break into the business. The key is to focus on a specific set of skills that you can provide and that others lack.
To illustrate, suppose you find a site that appears to be getting lots of traffic, but is not making a compelling offer with attractive bonuses. Well, if you can develop a great bonus offer that will complement that product, then you can help to generate more sales and earn a piece of the profits.
Finding a JV partnership that will work for you will mean some objective self-assessment. Being as honest as possible, note your strengths and weaknesses.
If your weaknesses in regards to affiliate marketing lie in skills that can be easily learned, then go ahead on your own. However, if you weaknesses are such that they will hamstring you, then consider finding a partner to work with.
Over time, you could develop your skills and strike out on your own, but until then you need some way to generate revenue.