When you sign a contract, you've voluntarily consented to its enforcement. When you're born, you've earned the right to your body, and I think the "involuntary" action is when someone violates this property right. When you trade your labor with someone else for property, you've voluntarily entered that relationship, and thus accrued right to that property (provided it wasn't previously stolen.) Land ownership is a more complicated issue. Your assertion about intellectual property is inaccurate, libertarians only believe in intellectual property rights protected by contract, not government.

I don't think libertarians believe in any collective. A collective is an abstraction. This is what trips people up. They think the "USA" is an entity, its not, its a collection of people. If I don't have the right to pull a gun on you and take your money, I don't get that right simply because I claim to be part of a collective.... but somehow many people feel that you do. Libertarians don't. Many people feel that if someone is part of a "government" or some other "collective" that this somehow gives them power over others they wouldn't have as individuals. An extreme example for counter argument is, do 5 guys get the right to rape a girl simply because they out number her and took a vote? Libertarians would say no. So, I don't think libertarians agree with "involuntary collective enforcement" in general.

>It's important how you define the initiation of force.

This is absolutely true. One thing that I've discovered is that many people I debate with think that using violence to accomplish ends they see as moral or justified is not an initiation of force (they'll even insist it is not violence.) This stumps me completely. I recognize where violence is, I feel, justified (namely in response to an initiation of force) and I'm willing to defend it. I don't have to pretend that it isn't what it is. And in the issues you bring up, some of them do bring up thorny areas (Which would require more debate than can fit here.) Abortion is the classic quandary... I'm pro-choice, but the nature of the issue makes it less cut and dry.

However, these are exceptions that prove the rule. Using the initiation of force as an indicator its easy to recognize the morality or immorality of many situations that seem to otherwise trip people up.

Everyone needs food, right? Should the government force people to work in fields to provide it, so that everyone in society is fed?