You can categorize most GNU/Linux distributions as either community or commercial. Community-based distributions like Debian, Fedora, or CentOS are maintained largely by volunteers and donations of services or money, while commercial distributions like Suse, Red Hat, or Xandros are backed by a company and compete directly against proprietary operating systems such as Windows and OS X.
Whether you are an individual or a corporate representative, the differences between the two categories are worth thinking about, because your choice can effect how you interact with them, the way you can expect them to conduct themselves, and the philosophies you face.
Admittedly, the distinction is less firm than it once was. A decade ago, members of community distributions were purists who viewed commercial distributions as upstarts that stole from the community and corrupted its ideals with business interests. In turn, those involved in commercial distributions tended to view members of community ones as naive, and their software offerings as needing proprietary extras to be suitable for use, or at least some business sense.
Now, the two categories are harder to tell apart. Several companies are involved with both commercial and community distributions -- for instance, Novell is involved with both Suse Linux Enterprise and openSUSE, and Red Hat with Red Hat Enterprise Linux and Fedora. In these cases, the two distros are technically separate, but business interests may spill over into the community distribution from time to time. Not only does Red Hat employ several Fedora community leaders, but, in its security crisis a couple of months ago, Red Hat seems to have made decisions that affected Fedora without consulting its board.
Even more confusing, while Ubuntu seems technically a community distribution, its backing by Canonical gives it more funding than the average community distribution. And, while some firmer distinction between Ubuntu and Canonical might evolve in the near future as Canonical increases its efforts at profitability, that hasn't happened yet. For now, both Ubuntu and Canonical continue to take direction from their founder Mark Shuttleworth.
In general, community and commercial distros are less polarized than they once were. Yet, even in cases where the boundaries are blurred, the distinction often holds true. You just have to remember that not to be surprised by exceptions to the general differences.
When commercial distributions launch, they are entering a market with well-established rules. Although they may challenge those rules by supporting a free software or open source philosophy, in other senses they have to conform to keep customers at ease.
One of the most obvious differences is accessibility to decision makers. Even in a giant community distribution like Debian, the project leader or the maintainer of a particular package is easily found on mailing lists or IRC channels, and any user can strike up a conversation with them. However, while the leaders of commercial distributions may be somewhat more accessible than their corporate peers, the larger the business, the harder it is for customers to engage them directly.
These days, for example, it is difficult to talk with any Red Hat employee outside of public relations or technical support without first obtaining the same sort of permission that you would need at Hewlett-Packard or Sun Microsystems -- and, even then, someone is likely to sit in on your exchange. The interaction is more formal and more restricted than in any community distribution.
However, the same formality makes approaching a commercial distribution much easier. Unless you are unusually obnoxious, the sole criteria for being heard by a commercial distribution is to be a customer or a potential customer.
By contrast, the programmer's ideal of a meritocracy still retains influence in a community distribution -- to say nothing of a lingering distrust here and there of anyone in business. While most community distributions have forums for new users, to really become accepted in them, you usually need to contribute in some way, regardless of whether you are a company or an individual. Making this kind of contribution can take time, and, if you are representing a business, community relations should probably be seen as a form of marketing. In effect, in a community distribution, you need to become part of the community. If initial contact is easier in a community distribution, long-term relationships are likely to require more maintenance.