Yes, this is a major reason that I doubt that donating to SIAI is a good idea. I feel that:

1. In order for existential risk charities to do a good job, they need good researchers and donors.

2. In order for existential risk charities to attract good researchers and donors, public interest in and concern for existential risk must grow substantially.

3. In light of point 2, the most important task for an existential risk charity right now is to increase public interest in and concern for existential risk.

4. SIAI seems poorly suited to generating interest in and concern for existential risk and may very well be lowering the prestige attached to investigating existential risk rather than raising the prestige attached to investigating existential risk.