Many things (for example user contributions, page history, user list) have a limit of 5000 items when accessed through the UI, by anyone, but only 500 when accessed through the API by a 'normal user' (by default, non-bot, non-sysop). This is inconsistent, and if anything is backwards since UI requests entail more work server-side. Moving (semi-)automated queries from UI to API, something that is presumably desired, can thus result in up to 10 times as many requests needing to be made, surely more than negating all benefit to both ends brought about by using the API in the first place.
If 5000 is too much, should the UI limit be reduced, if not, should the API limit be raised? If the worry is that the API lends itself more easily to rapid queries, perhaps some sort of rate limit should be introduced for expensive queries?