Rashi: Regarding Be'er-Sheva it does not say Lo Savo'u or Lo Sidreshu, rather, "Al Ta'avoru." There was not idolatry there. Rather, whenever someone from the 10 tribes went out to seek, and he did not pass Be'er-Sheva, he could still turn to the Beis ha'Mikdash, to Yerushalayim. Once he passed Be'er-Sheva, the road was to the calf in Beis Kel or the calf in Dan ? "Chei Elohecha v'Chei Derech Be'er-Sheva" (Amos 8:14). Verses decree punishments on Gilgal and Beis Kel, but not on Be'er-Sheva [for there was not idolatry there].

Radak (4:4 and here): It mentions Beis Kel, for the calf was there. It mentions Be'er-Sheva, for since it was the end of the border of Eretz Yisrael ("mi'Dan v'Ad Be'er-Shava" - Melachim I, 5:5), false Nevi'im instructed them to build there Mizbechos to idolatry - "Chei Elohecha v'Chei Derech Be'er-Sheva."

Malbim: Above, they announced "Bo'u Beis Kel u'Fish'u ha'Gilgal Harbu Lifsho'a" (4:4). Due to this, Hashem was angry at them, and struck them with hunger, plague and the sword, until only a 10th remained. Do not seek Beis Kel (people sought the calf there). The path to Beis Kel was via Be'er-Sheva.

Malbim: There they did other abominations and sinned greatly - "Kol Ra'asam ba'Gilgal" (Hoshe'a 9:15), "ha'Gilgal Harbu Lifsho'a" (Amos 4:4)..

Rashi: Its curse is like its name (Galo is like Gilgal). Radak ? we find "v'Ekron Te'aker" (Tzefanyah 2:4).

Malbim: Do not go to Gilgal, for it will be exiled; you will not find there life and salvation.

Rashi: Also Beis Kel, its curse is like its name. There is a city near it called Beis Aven (Yehoshua 18:12; therefore, its curse it to be Aven).

Rashi and Radak citing Targum Yonasan: Those who served idolatry of Beis Kel will be li'Lmah. The Targum of Hevel (nothingness) is Lemah. We find like this ? "Im Gil'ad Aven Ach Shav Hayu" (Hoshe'a 12:12).

Radak: They called Beis Kel 'Beis Aven' for disgrace, for it will be l'Aven and l'Ayin (for sin and nothing).