One of the things that is annoying for communities is when the spammers come and when the people join that ask really annoying and sometimes even stupid questions (yes there are stupid questions). However even if this is a downside that a community has to handle these kind of people, it is also a sign of maturity.
Since spammers wont do anything on a community where there is no conversion opportunity. Spam is a high volume, low conversion business so it needs an audience. This audience can be either the community members or search engines, the latter mainly used then for link building in a non ethical way.
Fools also arrive as your community becomes more mainstream. Most communities start in a rather niche like way: very focused on a single or a few topics, often only attracting other people with the same niche interests, REsulting in a lot of knowledgable people talking about a subjects and making the community a valuable source for information. Which in itself will attract new users, including those who are not really knowledgable about this topic and are seen as fools and who are asking the stupid questions.
If you are measuring success of your community, you might want to measure it based on the numbers of spammers you have, since this will indicate your reach and attractiveness for conversion. Also you might want to include the number of obvious questions asked, since this will indicate how much new members you will attract that are interested in the topic, but not really passionate, you might say the typical mainstream audience.