I supsect there is more to this question. It's easy to say, "I love you". What it sounds like to me is a person has doubts their feelings will be reciprocated. The only fear anyone has about expressing their love is the other person does not feel the same way about them. This is especially true if their relationship is a "platonic one".
One of the reasons I have never bought into the "lets be friends first" approach to dating is because it's difficult to get out of the "friendship box". In fact the vast majority of people who are attracted to someone let it be known up front and go right into dating if the attraction is "mutual". When someone says let be friends and see how it goes... what they're really saying is "I'm not quite feeling you romantically". However I do (like) you as a person.
The risk in saying "I love you" to someone you have a plantonic relationship with is in knowing it will forever change the nature of your relationship. Either they will want to move forward romantically with you or they will feel they need to distance themselves from you. It takes courage to go after what you want. I'd rather know if I stand a chance than to continue silently pining over someone. How you "approach" saying "I love you" is not going to effect whether or not the other person feels the same way about you.