Yes, long-time blogger here...
It is customary to ask permission before posting someone's link on your blog. In many cases, the person whose link you are posting has a right to know and should have the option to link exchange with you - you link to them, they link to you.
I've never posted a link in my "Friends" column without asking someone first.
I was taught this etiquette by a fellow blogger and fellow librarian back when I had a Library Science blog in 2001-2002.
I assume the rule still applies today?
"They're only crayons. You didn't fear them in kindergarten, why fear them now?" ~ Hugh MacLeod