I've noticed a distinct decline in operational LUGs. In my area (Seattle / Tacoma), most have closed up shop, and those that still have functioning web sites and email lists have very little traffic. Many of the web sites seem to exist only because the domain has not yet expired.

Is this an actual trend? Or am I not looking hard enough?

I cannot speak to trends; only to my experience. The Southeast Michigan LUG (www.semilinux.org) seems to be doing well.

I know that my LUG is going strong, but perhaps is not as large as it used to be. I've only been a member for three years, since I moved to this area, but that's the impression I get.

I have heard some folks theorize that Linux has gotten so much easier to install and to use than it was, say, 10 or 15 years ago, and that online help has gotten so much easier to find that there is less incentive for new users to seek out user groups. "Install fests," which used to be a staple for LUGs, are not very frequent any more.

This is a general observation:

One of the things I've noticed with groups like LUGs (sociologists call them "voluntary associations") is that there are often two or three persons who are the moving spirits keeping them going. When those persons run out of energy, move away, lose interest (admittedly not likely with a Linux geek), or even pass away, and no one is there to replace them, the group often peters out in a relatively short time.

If there's a demand, a new group will form to take its place.

well, not being "hard core" (unlike my father who has 4 machines with multiple distros), I've stuck with Red Hat since v9, moved to RHEL and then CentOS, and never had issues installing. But like I said, I'm not "adventurous". No Slackware for me.

Don't need to be adventurous to use Slackware unlike some less stable or changeable offerings.

I find that CUG's in general are declining. Computers and their accoutrements once were a hobby of a enthusiast sub group but as they have become more an more household appliances, the culture surrounding them has changed. Coupled with increased on-line access via the Internet, person-to-person groups and clubs are declining.

I agree with frankbell's analysys.
Anyway the problem is how to keep alive a LUG that has less and less members.
More in general: Have "physical" LUGs still a usefulness or by now we have to talk only about great online group?

Many LUGs seem to be replaced, in terms of getting warm bodies at a common location, with linux conventions. Where I'm "near" there's a ctlug mailing list and it's still lightly active. It used to get together at a physical location almost monthly. But you're more likely to meet at the annual convention than an actual LUG meeting these days.

When I used to live in south Florida, there was a LUG that was vigorously kept alive by enthusiasts and held regular meetings. That went on for years, and then 2 years ago it died off.
Local LUG in New Mexico, where I live now, seems to be doing pretty well (though I am yet to attend one of their meetings) from I can gather from their website.
I agree there is a general trend towards duying off of LUGs. Online meetings can't replace in- person gatherings, in my opinion. It may be more convenient, but the "magic" of in- person meetings just isn't there with meetings online.

The Lugs have not died they just closed psycialy and reborn on the internet as virtual only lugs.
But there are still a few around, i really prefer to have a real Lug with a premises where you can meet once a month for a coffee or maybe a beer and discuss not only linux related stuff it can be any of interest.

Maybe have an internet connection with a few home built server from leftover computers, the problem is to be able to do that some fee is required for rent electricity.
And not all are so found of paying a membership fee.

I have a cousin that is a member of an Atari enthusiasts' group. They "solve the membership fee problem" by holding their monthly meetings in a pizza joint. Of course, it is not a solution if one thing done at the meetings is using computers.

Its also a solution.

LUGs can also use community rooms at libraries and community centers, and sometimes city halls.

Here's a question: Is Linux now too "mainstream" for lugs? Many distros no longer take much effort to install and configure on most computers, and say what you will about Ubuntu, but it is very "consumer friendly".

With Steam now developing a Linux distro for their content, perhaps the last piece of the puzzle is both more consumer software for Linux. For the most part Linux installers and package formats have been distilled down to a few systems that work well for idiots like me, software instillation is no longer much of an issue beyond distro peculiarities and dependency issues.

There must be some lugs on the universities of some kind?

Tell me about it, i still have my Atari 1040ST laying around.

Yes, and I'd be shocked if that's not the only place where LUGs will continue to operate. I'm a student at WPI in Worcester, MA and our LUG is sponsored by the university.

LUGs may be declining in popularity because of the events that hold (or, rather, the events they don't hold). I know there was good turnout at a talk given by Jim Gettys about buffer bloat a few months back, but that talk was considered a "special event" and isn't typical of our LUG meetings. Just having discussions about Linux or asking for help now usually means going to the Internet, not trying to find other Linux users in your area.