I've been reading studies on how using the Internet is affecting people's lives in terms of social relationships, community commitment, and psychological well-being. Although I'm reading this for a class, the results of the studies are relevant to me as a blogger and blog-reader.
Most studies show that time spent on-line forming relationships often displaces face-to-face relationships with family and your own community. On-line relationships are weaker on average than those formed and maintained off-line. On-line friends, because they are not embedded in the same day-to-day environment, are less likely to provide tangible support (like a small loan, rides, or baby-sitting) and less likely to understand the context of your life. People can form strong relationships on-line, but they are rare.
Application: Don't spend more time and attention on weak ties at the expense of what should be strong ties in the real-world.
Although this wasn't included in the studies, I'd like to point out another healthy precaution with the Internet--watch your doctrine closely. In the blogosphere you will come across more arguments for and against every conceivable theological position than you ever would encounter in real life. Just thinking back to the last week, blogs I enjoy have surprised me by denouncing inerrancy and a 6-day Creation.
As threatening as higher criticism was for pastors in the 19th and 20th centuries, the "wider criticism" provided by the Internet may be more dangerous to the laity. As a general rule, when it comes to theology, don't talk to strangers.