Yes, there is a limit on the number of tags which you can add to a Flickr photo. Flickr allows you to tag your photos, so that you can easily add people to your photo's title & your comments by adding the @ sign. Tag is like a keyword which helps you to find things. You can add up to 75 tags to each photo or video. If you want to add more than 75 tags to a photo, then you will need to get the number of tags under that limit first.
You can install PicBackMan's Flickr uploader for Mac from the website and start backing up photos and videos.
Quick Tip to Keep your Photos Safe
Making backups of your photos & videos is a chore you probably skip, but it really doesn't have to be hard. Here's an effortless way to backup photos - PicBackMan. PicBackMan is the easiest and simplest way to keep your photos safely backed up in one or more online accounts. Simply download PicBackMan (it's free!), register your account, connect to your online store and tell PicBackMan where your photos are - PicBackMan does the rest, automatically. It bulk uploads all photos and keeps looking for new ones and uploads those too. You don't have to ever touch it.