I just had to post a thought on this topic.
I am still shocked 6 months after a friends wedding that after asking me to be a bridesmaid in her almost exclusively family wedding, she requested that I didn't bring a guest.
This was particularly akward since the wedding was on Sunday evening, the rehearsal was on Friday night. I was flying in & paying handsomely for the 3 nights in the hotel she chose. This doesn't count the dress, the bachelorette party in NYC, or any gifts. I was completely hurt that she would feel it was ok to expect me to spend well over $1K on being at her wedding, and yet she wasn't willing to foot the bill for an additional meal so I could have some company on the rest of the trip, and someone to sit next to at the reception.
Everything I read online says its ok to not invite a guest alongside a single guest. I agree with that thought in general, but I do feel that if you are a part of the wedding party, it seems plain cheap to expect them to spend money on your event, and you not offer the courtesy of them having a companion to dance with.
Just wanted to offer that up for those decided to guest or not to guest.
Thanks!