Now, I remember, when I first started hosting a server, I had no plugins. This was back in 1.5, and even happened once in 1.2.5. With both versions I ran a fine and moderate server. Rare lag. When I found about plugins, which was in 1.6, I started getting a ton of them. (Probably around 30) I couldn't help myself. I mean, honestly , just look at Bukkit's list of plugins! I was overwhelmed, there was so many plugins. I invited my friend to play one day and I looked in my console. It kept having the "Can't keep up!" message. I was devastated and my friend and I could barely place a flower. I took them all away and we were fine again. Later on in the updates I chose Wisely
of what plugins I had put on the server.

Plugins are amazing, and the developers do a fantastic job on them, but you can't just choose all the ones you like.
In most cases you can, but it all depends on your specs. Sometimes people choose random, useless plugins and they actually do impact on the server. I know of about 15 servers with this issue, and it's really starting to get irritating. Most servers do have a fair number of plugins, but other posts that say like "join now lolXDDD we have 67 plugins omfg we rok XDDD" and the server isn't even accessible (with the exception of "localhost") to anybody.

I don't know, it's just that choosing necessary AND fun plugins at the same time is better.
Please, choose plugins Wisely.