As enrollment in President Obama's health care program enters its third day, its network of insurance exchanges is still plagued by glitches along the lines of what I described in my column this week.

My Thursday morning attempt to login to the main hub that’s supposed to serve residents of 36 states, was greeted with a 404 error: “The requested URL /serverdown.html was not found.”

Defenders of the health care law argue that early glitches were inevitable and will be worked out and note that plans don't actually kick in until Jan. 1 and the open enrollment period goes through March. The even more optimistic spin is that the problems are due to high traffic, suggesting overwhelming demand for Obamacare.

I’d agree that critics of Obamacare should avoid calling the program a failure based on its rocky opening week, as there is still time to get these technological issues fixed without it severely impacting the law’s implementation.

But at what point do these glitches start to spell trouble?

It’s important to keep in mind that experts believe that to be viable, an exchange needs to have 100,000 participants. If the glitches continue, it could discourage people from applying. The bigger question for the program’s sustainability is not just how many people apply, but who applies and how that could affect the risk pool.

Roughly 40 percent of enrollees in the exchanges will need to be young and healthy so that they can offset the cost of covering sicker patients and those with pre-existing conditions. Those with extremely high medical expenses are the most likely to endure whatever technical hurdles arise and keep trying until they’re able to successfully enroll. But those who are more ambivalent — the young and healthy with low medical expenses — could get discouraged. That would have disastrous consequences for the law.

For all of the outreach efforts by the administration and outside groups, word of mouth is likely to be the most powerful factor influencing people’s decisions about accessing the exchanges. The administration wants to get to the point where, if a bunch of friends in their 20s are talking about health insurance, one will say, “Oh, I went on that new Obamacare exchange and it was really easy and I was able to get affordable insurance, I’ll send you the link.” But instead, if too many people say, “I tried to buy insurance but the website was barely functional, and when I finally searched the plans they were more expensive than I thought,” it’s really going to dampen enrollment.

Beyond this, one issue is that the glitches that have been publicized are ones that are easily noticeable -- basic functions like trying to get a page to load, register, or log in to the system. But as Reason's Peter Suderman pointed out, these functions are pretty easy compared to the huge technological challenge of getting state and federal databases to communicate with one another to determine eligibility and calculate the subsidies that individuals qualify for under the law. If the bugs facing Obamacare are anything like roaches, for every one that is visible, there could be a lot more hidden.

So, three days in, it’s too early for critics of Obamacare to proclaim that the glitches prove it’s doomed to fail. But I also don’t think supporters of the law should be getting cocky and assume that everything will get fixed and enrollment will be a smashing success, either.