Careful while installing Plugins
The best feature of hosted Wordpress is the vast number of plugins available. Last week I downloaded a few of them from Plugin Database and installed all of them in the plugins directory. After installing these plugins, when I activated all of them, there was some problem with my site while loading. My blog was displaying a php page!. I was really surprised to see this and I tried to refresh the page, but still it was showing me a php page. I scrolled down and saw that my blog was actually loading below this php page.
I knew it was because of one of the plugins installed by me. So I clicked on the plugins page in the Wordpress to deactivate it. But to my surprise, the Wordpress was also showing me the same php page and it was loading after below this php page and that too not completely.
Now I knew it was not possible to deactivate it from Wordpress. So I logged into my server and deleted all the plugin files which I had uploaded that day. After deleting these files, everything was back to normal, Wordpress and blog were loading properly.
I had another issue with an Ajax based plugin, this time it was showing Javascript error when I activate the plugin. This was pointed to me by one of the readers.
From the vast list of plugins, its really difficult to identify which one is error free. 
You are 100% right. Some Wordpress plugins are problematic, and the only way to uninstall them is via the hosting control pannel. That’s why i try to ask others in the blogsphere for their thoughts before installing.
Gili
You’ve already been added to 2kbloggers.com. Thanks.
You are right man , i hate these php errors . Once i was trying to modify a plugin and after updating i faced a PHP parse error , so i had to delete the file through FTP .
I am running a PR6 blog for a client of mine. Since I have some experience in MySQL, I happen to see how wordpress is doing. Surprisingly, Wordpress uses an awful lot of queries to the database. Most of this was attributed to the plug-ins used in that site.
I ended up in using two cache mechanism to get a decent performance out of that.