Risk Management in a start up

Someone suggested those start up company should focus what they are good at. Well, i got a different point of view. We have a variety set of business area. This spread out the risk. Even one area is not running profit, other business areas can support the company running.
Moreover, the one area can generate some new leads. For example , we sold a web design package to a client. Once times I have chats with that client, i found they need someone to do some I.T. support tasks.  Well, i got some new businesses.
I think that is good to develop some new business areas along your core business line.