High process count - is this normal? and what's up with 10.6.6?

Question

Among other aspects of the general weirdness I've noticed occurring on my machine (which seems to have started around when I installed 10.6.6), I've noticed that the PID numbers in Activity Monitor have recently skyrocketed. I used to go for two weeks or a month before seeing PID numbers in the 30-50k range (and even that is high in comparison to a year or two ago), but now they're much higher, much sooner.
For example: it's been 2 days and an hour since my last reboot (according to uptime), and I'm now showing processes in the mid 99k range. I have several background apps installed, but still—99 thousand processes come and gone in just over two days? Seriously? Given what I remember as normal over the past couple of years, this seems insanely high.
Again, given this and the other weirdness I've had (mainly sluggishness), seemingly since around when I installed 10.6.6, it makes me wonder what is going on. I've got 4 GB of RAM and over 50 GB of free HD space; the computer uses only about 1 GB of that following a fresh boot (Safari seems to be the biggest RAM hog, partially because of extensions, so I try to quit it fairly regularly). Is 10.6.6 a buggy release or something?
Any thoughts on what might be going on (mainly for the PID thing but also the general weirdness) would be greatly appreciated. Thanks!
Background apps installed: Sophos AntiVirus, TechTool Pro, Dropbox, FlashFrozen, MenuPop, OpenDNS Updater, Growl, MagiCal, SIMBL. Most of these, notably Sophos and SIMBL, were installed before this sluggishness started.

Answer 1

Thanks. I read through the Console logs, and I only found a few things that seemed to repeat. A lot of entries similar to this one:
Feb 28 08:57:45 [computer-name] [0x0-0x17d17d].com.apple.Safari[83590]: objc
[83590]: Class SUStandardVersionComparator is implemented in both /Library/
Application Support/SIMBL/Plugins/Safari AdBlocker.bundle/Contents/MacOS/../
Frameworks/Sparkle.framework/Versions/A/Sparkle and /Library/Application
Support/SIMBL/Plugins/Safari Cookies.bundle/Contents/MacOS/../Frameworks/
Sparkle.framework/Versions/A/Sparkle. One of the two will be used. Which one
is undefined.
And this one:
Mar 1 14:11:53 [computer-name] [0x0-0x2c82c8].com.apple.Safari[53329]: objc
[53329]: Class SUAppcastItem is implemented in both /Library/Application
Support/SIMBL/Plugins/Safari AdBlocker.bundle/Contents/MacOS/../Frameworks/
Sparkle.framework/Versions/A/Sparkle and /Users/me/Library/Internet Plug-Ins/
ClickToFlash.webplugin/Contents/Frameworks/Sparkle.framework/Sparkle. One of
the two will be used. Which one is undefined.
Many of these:
Feb 28 23:40:28 [computer-name] com.apple.WebKit.PluginAgent[8588]: 2011-02-28
23:40:28.764 WebKitPluginHost[11565:2c113] * __NSAutoreleaseNoPool(): Object
0xa08cd808 of class NSCFBoolean autoreleased with no pool in place - just
leaking
And a small handful of these:
Mar 5 20:35:12 [computer-name] loginwindow[30]: in pamsmauthenticate(): Failed to
determine Kerberos principal name.
Although I think the WebKit entries would seem to explain the VM churning I've had lately (I don't think I mentioned that earlier because it seems unrelated; turning off Safari extensions makes it go away)—so I'm playing with which extensions I have turned on and off to try to figure that out—those messages don't seem to suggest something which is (re)starting a ton of processes. I read through that page you referred me to and searched the logs for those terms (like "exited with code", "throttling respawn", etc.), but nothing came up.
I checked the launchagents folders, as the page suggested, and in my personal folder, I have a launch agent for gconsync (Google Contact Sync), and in the /Library folder, I have ones for GoogleSoftwareUpdateAgent, Micromat's TechtoolProAgent, and SIMBL. Other than the duplicated functionality messages related to SIMBL, none of the others show excessive messages (or many at all, for that matter).
I know what you're saying about the lack of viruses, but I must admit that I'm surprised to hear that people are having trouble with Sophos. I'm familiar with the behavior of anti-virus software on Windows (performance killer), and I remember being not so thrilled with NAV 8 and 10, which I had installed years and years ago on an old machine, so I thought I'd try out Sophos, be unimpressed, and get rid of it. On the contrary, it has been the most unobtrusive, least bothersome anti-virus app I've ever seen. I haven't felt a performance drag from it since I installed it (it's been several months), and haven't seen anything weird that I could specifically link to Sophos. I decided to search the logs for "sophos" to see if something bad was happening behind the scenes, but all that came up was a handful of installer entries for virus updates.
I have a nagging hunch that maaaaybe this has something to do with a Safari extension gone wild. I find it hard to believe that extensions would be capable of intentionally spawning processes, but what about unintentionally somehow? Hmm...
Anyway, any thoughts? Much appreciated!