It is a secondary issue if individual users can hack the system to gain somewhat undeserved reputation.
The primary issue for the quality of Stackoverflow is whether good answers are generated, and whether the best (most correct, relevant and informative) answers float to the top. This seems to be the case AFAICT, so I don't think this reputation gaming is a big problem for the site. (It will be a big problem for somebody (theoretical) who hired people based on Stackoverflow reputation. But that would be stupid anyway.)
The primary issue for the quality of Stackoverflow is whether good answers are generated, and whether the best (most correct, relevant and informative) answers float to the top. This seems to be the case AFAICT, so I don't think this reputation gaming is a big problem for the site. (It will be a big problem for somebody (theoretical) who hired people based on Stackoverflow reputation. But that would be stupid anyway.)