I actually came across a GMAT question in a Kaplan book I'm borrowing which seems strikingly similar to the Oakland Athletics situation right now.  It goes like this.

---Start of Analysis Essay Question---
Home Attendance at NY Mammoth games is significantly lower now than it was during their championship years in the mid-seventies.  Many fans are fearful of the Dockside neighborhood around Mammoth Field.  In view of the attendance decline, it is clear that the team should move.

Explain how logically persuasive you find this argument.  In discussing your viewpoint, analyze the argument's line of reasoning and its use of evidence.  Also explain what, if anything, would make the argument more valid and convincing or help you to better evaluate its conclusion.
---End of Essay Questions---

Kaplan considers this a perfect score 6/6.

---Start of Answer---
This argument is extremely unpersuasive for several reasons.  Its main weakness is the huge gap between the evidence and conclusion.  The conclusion is that the team should move.  The evidence presented, however, simply does not warrant such an extreme course of action.  Assuming that the character of the neighborhood of Dockside is indeed to blame for the Mammoths' poor attendance, there are at least two alternative courses of action the team could pursue.  First, the team's ownership could encourage city officials to devote funds to improving Dockside.  If such efforts successfully renovated the neighborhood, more fans might attend Mammoth games.  Second, even if improving Dockside wouldn't be sufficient to increase attendance, the team could simply move to another, better neighborhood in the same city.  There is no reason to think that this far less drastic action wouldn't have at least as strong an impact on attendance.  In short, the argument is extremely weak because it neglects to consider alternative solutions to the problem of low attendance.

There is an additional flaw to be found in the argument's evidence.  By asserting that today's attendance is "lower than during the championship years," the argument actually implies that Dockside is not the problem.  The conclusion is based on the claim that the neighborhood is responsible for falling attendance.  Yet perhaps fans aren't attending Mammoth games because the team just isn't playing as well as it once did.  If that is the case, then moving the team elsewhere is unlikely to improve attendance rates, since the problem lies not with the games' location but with their quality.  So the argument suffers from two major flaws: the cause of the decline in attendance is ill-supported, as is the recommended solution.  Strengthening the argument would require showing, first of all, that the team's poor playing is not the real reason for poor attendance, and secondly, that the neither of the two alternative solutions discussed above would solve the problem.
---End of perfect score answer---

Additional valid arguments I think that were omitted.

Is the sport in a decline?
Is the stadium up to par?
Is their new or increased competition in the market?

So why don't the A's sellout?  
Because the city of Oakland is on a decline?
Because the sport wasn't as popular now than the Haas years?
Because the stadium isn't that great?
Because the A's are competing against a brand new stadium a few miles by them?
Because we haven't won a World Series recently?

I guess the better question would be, what can the Athletics do to sell more tickets sustainably to the present and future?