[sluukkonen]

Here's one example. Web browsers often use bloom filters or similar data structures to check for malicious URLs. They first check the URL against the local bloom filter, and if a match is found, they double check against an online API to make sure it wasn't a false positive.

Shipping a full list of malicious URLs would be too expensive, but a bloom filter fits in a fraction of the space and can still eliminate a vast majority of the API calls.

[loeg]

They're useful in cases like this, where the set of entries is much smaller than the total set size (e.g., all URLs). Once you approach sets with 50% membership, a bitset becomes more efficient (accuracy per space) than a bloom filter or any other probabilistic structure.

[donatj]

Interesting. I may in fact have a use for that.