You'll run into a few problems here and there, some of them out of your control and some of them within your control.  I'll break this down into technical problems and people problems.

On the technical end of things, it's a fact of life that occasionally parts of the Internet go down for a bit.  It could be the actual server the files are on, one of the main national pipelines, any of the major hubs along the way (often over ten of them), your local ISP — or, more likely — some catastrophic mishap completely out of everyone's control.

I once belonged to a national ISP called PrimeNet.  They had a page on their site of 'current outages'.  It was just stunning how many of them were completely out of PrimeNet's control (flash flood washes out a power line, bulldozer rips up a fiber-optics cable, etc) — but you just know who everybody blamed when their precious Internet connection went down.

When it comes to spam in your comments, there are tons of free anti-spam plugins on the WordPress site.  Many of them stay current by hooking up to an online database.  There are also plugins that force the commenter to type in graphic characters before leaving the comment, which should be very effective.  The WordPress forum will have the latest poop if you run into any specific hassles.

For help on anything else, you need Google or a forum:

WordPress Forum	Tavern Forum
Designpraxis Forum	Bloggeries Forum

Google tips:

• Write it out just like you were asking it in a forum, since that's what you're looking for; someone who's already asked the question.
   
• If you're getting an error message with your problem, put it in quotes so it'll search for that exact phrase.
   
• Forum pages are sometimes quite long, so rather than just clicking on the Google link, click on the 'Cached' link so your keywords will be highlighted.

Forum tips:

• You want an active forum.  Look at the number of responses the posts are getting and the dates.
   
• Do a site search first.  Most likely somebody else has asked the same question.
   
• Put the basic problem in the post's title.
   
• Lay it out it two parts, a quick synopsis and full details.
   
• End it courteously, like "Thanks very much for any help."

I can assure you, the real pros just live for nasty, gnarly problems, so don't give up if you don't get an immediate response.  Ask again a few days later, and again be courteous, saying something like, "Sorry for the repeat request, but this is really important to me."  Almost everyone gets answered if they're persistent enough.  It's usually just a matter of good timing and having your message being displayed when the right person comes along.
 

People Problems

You might have the occasional disruptive member.  The line between 'argumentative' and 'troll' is pretty clear.  Once they cross that line and pointedly go against your expressed (and officially posted) wishes ("no vile swearing", "no racist remarks", etc), then you shouldn't have any hesitancy in banning them from the comments.  They'd do the same to you.

What's interesting is that while some trolls are purposefully disruptive if you blog on politics because they're viewing it as "battling the enemy" in their ideological little world, there's another sort who views the whole thing thusly:

1. We have "freedom of speech" here in America.

2. Therefore, because the blog site is in America, you can say whatever you want on it.

Of course, if you explain that's not qui-i-ite how it works, you're promptly branded a Nazi by the troll and his sympathizers.  It'll be portrayed as "the little guy just wanting to voice his opinion versus the mean, evil, tyrannical blogger."  Just ban his sorry ass and eventually his loyal supporters will forget about him.  If they don't, ban their sorry asses as well.  There are too many readers out there to bother with some vociferous vocal minority, and trolls drive smart commenters away.

On the other hand, if you write on political matters, it's not a bad idea to have a few token members of the opposing party around, just to keep you on your toes.  Their sudden lack of response in the comments means you've just made a telling point in the post, no?
 

Another people problem is 'sockpuppeting', or logging in using other handles, usually to support something their first persona just said in a comment.  "You're so right!  That's brilliant of you!"  If I noticed (by IP address) that some commenter was sockpuppeting his comments like the above, I'd deem it fairly harmless and probably let it go, or leave some lighthearted comment that would subtly indicate I was onto him.  If, however, it was some troll sockpuppeting himself to support a bunch of racist/sexist/ageist/etc-ist comments he'd left, then that's worthy of a warning, if not outright banishment.

On the subject, on the 'Email' page I mention a 'throwaway' address, where it wouldn't matter if it ended up on some spam list.  This would also be the address you'd use if using email to warn a commenter that he's on probation.  If he wants to lash back, the first thing he'll do is put the return email address on every nasty list he can find.

Again, you don't want to get hung up fretting over a couple of readers.  I'd hesitate to coldly call blogging "a numbers game", but it's certainly closer to that than a "trying to please everyone" game.  You'll never do that, and you shouldn't even try.

Bottom line is, it's your site and you can run it however you like.  If something's annoying you, do something about it.  If the comments are creating more negativity than positiveness, eliminate them or make the comments for pre-approved members only.  If there's something about the theme you don't like, either fix it or replace it.  If a plugin isn't working correctly, go find one that does.  Overall, your blogging adventure should be a positive experience.  If it's not, fix it and make it so.