Here's the thing. It doesn't matter how good a contractor/freelancer is, unless they've worked with us regularly, and know the rest of our team "intimately", they're not usually as effective as our full time staff. 

At Fudge, we use external resources only when it's absolutely essential. Partly for financial reasons, but mostly because they're just not as effective as full time staff.

Our Scrum teams are made up of specialists, all with varying levels of experience. One thing that they have in common is their familiarity with the rest of the team. On average, we've worked with each other day-in-day-out for at least 3 years. That's 8 hours a day, for three years.

Communication

A team that spends most of their working day together knows how the rest of the team thinks and behaves. If someone's grumpy, they'll know to either leave them alone, or they'll know what to say to cheer them up. They understand the strengths and weaknesses within the team, so if someone's stuck, they'll know who to ask for help.

Through no fault of their own, temporary additions to the team don't have this understanding. You can only get that by spending time with each other.

Accountability/Responsibility

This is a big one. Scrum encourages the team to take collective responsibility for the project. If something's going wrong, we don't blame someone, we figure it out together. When we start a project, we build a team around it that'll be there from start to end. Part time outsiders cause problems:

• They probably aren't familiar with the general history of the project
• They won't know the client personally
• They don't have as much of an interest in the success of the project beyond their contract period

Performance

We work quickly at Fudge. We can do this because we've been working together day in, day out for years. We know who's good at particular things and how quickly they might be able to complete a task. Scrum is a major reason for the speed that we work, but mostly, it's the personal familiarity that Scrum has encouraged. External people may work quickly independently, but without knowing our processes and personal traits, they usually slow the team down.

Conclusion

I read somewhere that if a team is working well, they'll have 'in-jokes'. They'll be able to have a conversation amongst themselves for ten minutes, and you won't have a clue what they're talking about. This is a good thing, trust me.