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If you see someone you admire from a blog, Twitter, etc. at a conference/party... Say hi! They expect to meet people. This is true if they have an audience of 5k, 50k or 500k+ But do try not to immediately put them on a pedestal. Don't present yourself as less-than; you're not.
It's great to bring up work/ideas of theirs that are meaningful to you, but it can be counterproductive and *sometimes* stressful for them if you focus on communicating the extent of their impact rather than the content. Talk about yourself, too. Ask real questions, ask for help!
Also: be cautious about this in contexts where they *wouldn't* expect to meet someone new, e.g. on the street, a grocery store. Say hi! But keep it brief. People are in a different head-space. If they invite convo, great! But they'll likely appreciate an assumption of brevity
I wonder from which side of your experience this is coming from 
Both, for sure
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